essay on hypothesis

How to Write a Hypothesis

If I [do something], then [this] will happen.

This basic statement/formula should be pretty familiar to all of you as it is the starting point of almost every scientific project or paper. It is a hypothesis – a statement that showcases what you “think” will happen during an experiment. This assumption is made based on the knowledge, facts, and data you already have.

How do you write a hypothesis? If you have a clear understanding of the proper structure of a hypothesis, you should not find it too hard to create one. However, if you have never written a hypothesis before, you might find it a bit frustrating. In this article from EssayPro - custom essay writing services , we are going to tell you everything you need to know about hypotheses, their types, and practical tips for writing them.

Hypothesis Definition

According to the definition, a hypothesis is an assumption one makes based on existing knowledge. To elaborate, it is a statement that translates the initial research question into a logical prediction shaped on the basis of available facts and evidence. To solve a specific problem, one first needs to identify the research problem (research question), conduct initial research, and set out to answer the given question by performing experiments and observing their outcomes. However, before one can move to the experimental part of the research, they should first identify what they expect to see for results. At this stage, a scientist makes an educated guess and writes a hypothesis that he or she is going to prove or refute in the course of their study.

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A hypothesis can also be seen as a form of development of knowledge. It is a well-grounded assumption put forward to clarify the properties and causes of the phenomena being studied.

As a rule, a hypothesis is formed based on a number of observations and examples that confirm it. This way, it looks plausible as it is backed up with some known information. The hypothesis is subsequently proved by turning it into an established fact or refuted (for example, by pointing out a counterexample), which allows it to attribute it to the category of false statements.

As a student, you may be asked to create a hypothesis statement as a part of your academic papers. Hypothesis-based approaches are commonly used among scientific academic works, including but not limited to research papers, theses, and dissertations.

Note that in some disciplines, a hypothesis statement is called a thesis statement. However, its essence and purpose remain unchanged – this statement aims to make an assumption regarding the outcomes of the investigation that will either be proved or refuted.

Characteristics and Sources of a Hypothesis

Now, as you know what a hypothesis is in a nutshell, let’s look at the key characteristics that define it:

• It has to be clear and accurate in order to look reliable.
• It has to be specific.
• There should be scope for further investigation and experiments.
• A hypothesis should be explained in simple language—while retaining its significance.
• If you are making a relational hypothesis, two essential elements you have to include are variables and the relationship between them.

The main sources of a hypothesis are:

• Scientific theories.
• Observations from previous studies and current experiences.
• The resemblance among different phenomena.
• General patterns that affect people’s thinking process.

Types of Hypothesis

Basically, there are two major types of scientific hypothesis: alternative and null.

• Alternative Hypothesis

This type of hypothesis is generally denoted as H1. This statement is used to identify the expected outcome of your research. According to the alternative hypothesis definition, this type of hypothesis can be further divided into two subcategories:

• Directional — a statement that explains the direction of the expected outcomes. Sometimes this type of hypothesis is used to study the relationship between variables rather than comparing between the groups.
• Non-directional — unlike the directional alternative hypothesis, a non-directional one does not imply a specific direction of the expected outcomes.

Now, let’s see an alternative hypothesis example for each type:

Directional: Attending more lectures will result in improved test scores among students. Non-directional: Lecture attendance will influence test scores among students.

Notice how in the directional hypothesis we specified that the attendance of more lectures will boost student’s performance on tests, whereas in the non-directional hypothesis we only stated that there is a relationship between the two variables (i.e. lecture attendance and students’ test scores) but did not specify whether the performance will improve or decrease.

• Null Hypothesis

This type of hypothesis is generally denoted as H0. This statement is the complete opposite of what you expect or predict will happen throughout the course of your study—meaning it is the opposite of your alternative hypothesis. Simply put, a null hypothesis claims that there is no exact or actual correlation between the variables defined in the hypothesis.

To give you a better idea of how to write a null hypothesis, here is a clear example: Lecture attendance has no effect on student’s test scores.

Both of these types of hypotheses provide specific clarifications and restatements of the research problem. The main difference between these hypotheses and a research problem is that the latter is just a question that can’t be tested, whereas hypotheses can.

Based on the alternative and null hypothesis examples provided earlier, we can conclude that the importance and main purpose of these hypotheses are that they deliver a rough description of the subject matter. The main purpose of these statements is to give an investigator a specific guess that can be directly tested in a study. Simply put, a hypothesis outlines the framework, scope, and direction for the study. Although null and alternative hypotheses are the major types, there are also a few more to keep in mind:

Research Hypothesis — a statement that is used to test the correlation between two or more variables.

For example: Eating vitamin-rich foods affects human health.

Simple Hypothesis — a statement used to indicate the correlation between one independent and one dependent variable.

For example: Eating more vegetables leads to better immunity.

Complex Hypothesis — a statement used to indicate the correlation between two or more independent variables and two or more dependent variables.

For example: Eating more fruits and vegetables leads to better immunity, weight loss, and lower risk of diseases.

Associative and Causal Hypothesis — an associative hypothesis is a statement used to indicate the correlation between variables under the scenario when a change in one variable inevitably changes the other variable. A causal hypothesis is a statement that highlights the cause and effect relationship between variables.

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Hypothesis vs Prediction

When speaking of hypotheses, another term that comes to mind is prediction. These two terms are often used interchangeably, which can be rather confusing. Although both a hypothesis and prediction can generally be defined as “guesses” and can be easy to confuse, these terms are different. The main difference between a hypothesis and a prediction is that the first is predominantly used in science, while the latter is most often used outside of science.

Simply put, a hypothesis is an intelligent assumption. It is a guess made regarding the nature of the unknown (or less known) phenomena based on existing knowledge, studies, and/or series of experiments, and is otherwise grounded by valid facts. The main purpose of a hypothesis is to use available facts to create a logical relationship between variables in order to provide a more precise scientific explanation. Additionally, hypotheses are statements that can be tested with further experiments. It is an assumption you make regarding the flow and outcome(s) of your research study.

A prediction, on the contrary, is a guess that often lacks grounding. Although, in theory, a prediction can be scientific, in most cases it is rather fictional—i.e. a pure guess that is not based on current knowledge and/or facts. As a rule, predictions are linked to foretelling events that may or may not occur in the future. Often, a person who makes predictions has little or no actual knowledge of the subject matter he or she makes the assumption about.

Another big difference between these terms is in the methodology used to prove each of them. A prediction can only be proven once. You can determine whether it is right or wrong only upon the occurrence or non-occurrence of the predicted event. A hypothesis, on the other hand, offers scope for further testing and experiments. Additionally, a hypothesis can be proven in multiple stages. This basically means that a single hypothesis can be proven or refuted numerous times by different scientists who use different scientific tools and methods.

To give you a better idea of how a hypothesis is different from a prediction, let’s look at the following examples:

Hypothesis: If I eat more vegetables and fruits, then I will lose weight faster.

This is a hypothesis because it is based on generally available knowledge (i.e. fruits and vegetables include fewer calories compared to other foods) and past experiences (i.e. people who give preference to healthier foods like fruits and vegetables are losing weight easier). It is still a guess, but it is based on facts and can be tested with an experiment.

Prediction: The end of the world will occur in 2023.

This is a prediction because it foretells future events. However, this assumption is fictional as it doesn’t have any actual grounded evidence supported by facts.

Based on everything that was said earlier and our examples, we can highlight the following key takeaways:

• A hypothesis, unlike a prediction, is a more intelligent assumption based on facts.
• Hypotheses define existing variables and analyze the relationship(s) between them.
• Predictions are most often fictional and lack grounding.
• A prediction is most often used to foretell events in the future.
• A prediction can only be proven once – when the predicted event occurs or doesn’t occur. 
• A hypothesis can remain a hypothesis even if one scientist has already proven or disproven it. Other scientists in the future can obtain a different result using other methods and tools.

We also recommend that you read about some informative essay topics .

Now, as you know what a hypothesis is, what types of it exist, and how it differs from a prediction, you are probably wondering how to state a hypothesis. In this section, we will guide you through the main stages of writing a good hypothesis and provide handy tips and examples to help you overcome this challenge:

1. Define Your Research Question

Here is one thing to keep in mind – regardless of the paper or project you are working on, the process should always start with asking the right research question. A perfect research question should be specific, clear, focused (meaning not too broad), and manageable.

Example: How does eating fruits and vegetables affect human health?

2. Conduct Your Basic Initial Research

As you already know, a hypothesis is an educated guess of the expected results and outcomes of an investigation. Thus, it is vital to collect some information before you can make this assumption.

At this stage, you should find an answer to your research question based on what has already been discovered. Search for facts, past studies, theories, etc. Based on the collected information, you should be able to make a logical and intelligent guess.

3. Formulate a Hypothesis

Based on the initial research, you should have a certain idea of what you may find throughout the course of your research. Use this knowledge to shape a clear and concise hypothesis.

Based on the type of project you are working on, and the type of hypothesis you are planning to use, you can restate your hypothesis in several different ways:

Non-directional: Eating fruits and vegetables will affect one’s human physical health. Directional: Eating fruits and vegetables will positively affect one’s human physical health. Null: Eating fruits and vegetables will have no effect on one’s human physical health.

4. Refine Your Hypothesis

Finally, the last stage of creating a good hypothesis is refining what you’ve got. During this step, you need to define whether your hypothesis:

• Has clear and relevant variables;
• Identifies the relationship between its variables;
• Is specific and testable;
• Suggests a predicted result of the investigation or experiment.

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Hypothesis Examples

Following a step-by-step guide and tips from our essay writers for hire , you should be able to create good hypotheses with ease. To give you a starting point, we have also compiled a list of different research questions with one hypothesis and one null hypothesis example for each:

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Sometimes, coping with a large academic load is just too much for a student to handle. Papers like research papers and dissertations can take too much time and effort to write, and, often, a hypothesis is a necessary starting point to get the task on track. Writing or editing a hypothesis is not as easy as it may seem. However, if you need help with forming it, the team at EssayPro is always ready to come to your rescue! If you’re feeling stuck, or don’t have enough time to cope with other tasks, don’t hesitate to send us you rewrite my essay for me or any other request.

is an expert in nursing and healthcare, with a strong background in history, law, and literature. Holding advanced degrees in nursing and public health, his analytical approach and comprehensive knowledge help students navigate complex topics. On EssayPro blog, Adam provides insightful articles on everything from historical analysis to the intricacies of healthcare policies. In his downtime, he enjoys historical documentaries and volunteering at local clinics.

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How to Write a Research Hypothesis: Good & Bad Examples

What is a research hypothesis?

A research hypothesis is an attempt at explaining a phenomenon or the relationships between phenomena/variables in the real world. Hypotheses are sometimes called “educated guesses”, but they are in fact (or let’s say they should be) based on previous observations, existing theories, scientific evidence, and logic. A research hypothesis is also not a prediction—rather, predictions are ( should be) based on clearly formulated hypotheses. For example, “We tested the hypothesis that KLF2 knockout mice would show deficiencies in heart development” is an assumption or prediction, not a hypothesis. 

The research hypothesis at the basis of this prediction is “the product of the KLF2 gene is involved in the development of the cardiovascular system in mice”—and this hypothesis is probably (hopefully) based on a clear observation, such as that mice with low levels of Kruppel-like factor 2 (which KLF2 codes for) seem to have heart problems. From this hypothesis, you can derive the idea that a mouse in which this particular gene does not function cannot develop a normal cardiovascular system, and then make the prediction that we started with. 

What is the difference between a hypothesis and a prediction?

You might think that these are very subtle differences, and you will certainly come across many publications that do not contain an actual hypothesis or do not make these distinctions correctly. But considering that the formulation and testing of hypotheses is an integral part of the scientific method, it is good to be aware of the concepts underlying this approach. The two hallmarks of a scientific hypothesis are falsifiability (an evaluation standard that was introduced by the philosopher of science Karl Popper in 1934) and testability —if you cannot use experiments or data to decide whether an idea is true or false, then it is not a hypothesis (or at least a very bad one).

So, in a nutshell, you (1) look at existing evidence/theories, (2) come up with a hypothesis, (3) make a prediction that allows you to (4) design an experiment or data analysis to test it, and (5) come to a conclusion. Of course, not all studies have hypotheses (there is also exploratory or hypothesis-generating research), and you do not necessarily have to state your hypothesis as such in your paper. 

But for the sake of understanding the principles of the scientific method, let’s first take a closer look at the different types of hypotheses that research articles refer to and then give you a step-by-step guide for how to formulate a strong hypothesis for your own paper.

Types of Research Hypotheses

Hypotheses can be simple , which means they describe the relationship between one single independent variable (the one you observe variations in or plan to manipulate) and one single dependent variable (the one you expect to be affected by the variations/manipulation). If there are more variables on either side, you are dealing with a complex hypothesis. You can also distinguish hypotheses according to the kind of relationship between the variables you are interested in (e.g., causal or associative ). But apart from these variations, we are usually interested in what is called the “alternative hypothesis” and, in contrast to that, the “null hypothesis”. If you think these two should be listed the other way round, then you are right, logically speaking—the alternative should surely come second. However, since this is the hypothesis we (as researchers) are usually interested in, let’s start from there.

Alternative Hypothesis

If you predict a relationship between two variables in your study, then the research hypothesis that you formulate to describe that relationship is your alternative hypothesis (usually H1 in statistical terms). The goal of your hypothesis testing is thus to demonstrate that there is sufficient evidence that supports the alternative hypothesis, rather than evidence for the possibility that there is no such relationship. The alternative hypothesis is usually the research hypothesis of a study and is based on the literature, previous observations, and widely known theories. 

Null Hypothesis

The hypothesis that describes the other possible outcome, that is, that your variables are not related, is the null hypothesis ( H0 ). Based on your findings, you choose between the two hypotheses—usually that means that if your prediction was correct, you reject the null hypothesis and accept the alternative. Make sure, however, that you are not getting lost at this step of the thinking process: If your prediction is that there will be no difference or change, then you are trying to find support for the null hypothesis and reject H1. 

Directional Hypothesis

While the null hypothesis is obviously “static”, the alternative hypothesis can specify a direction for the observed relationship between variables—for example, that mice with higher expression levels of a certain protein are more active than those with lower levels. This is then called a one-tailed hypothesis. 

Another example for a directional one-tailed alternative hypothesis would be that 

H1: Attending private classes before important exams has a positive effect on performance. 

Your null hypothesis would then be that

H0: Attending private classes before important exams has no/a negative effect on performance.

Nondirectional Hypothesis

A nondirectional hypothesis does not specify the direction of the potentially observed effect, only that there is a relationship between the studied variables—this is called a two-tailed hypothesis. For instance, if you are studying a new drug that has shown some effects on pathways involved in a certain condition (e.g., anxiety) in vitro in the lab, but you can’t say for sure whether it will have the same effects in an animal model or maybe induce other/side effects that you can’t predict and potentially increase anxiety levels instead, you could state the two hypotheses like this:

H1: The only lab-tested drug (somehow) affects anxiety levels in an anxiety mouse model.

You then test this nondirectional alternative hypothesis against the null hypothesis:

H0: The only lab-tested drug has no effect on anxiety levels in an anxiety mouse model.

How to Write a Hypothesis for a Research Paper

Now that we understand the important distinctions between different kinds of research hypotheses, let’s look at a simple process of how to write a hypothesis.

Writing a Hypothesis Step:1

Ask a question, based on earlier research. Research always starts with a question, but one that takes into account what is already known about a topic or phenomenon. For example, if you are interested in whether people who have pets are happier than those who don’t, do a literature search and find out what has already been demonstrated. You will probably realize that yes, there is quite a bit of research that shows a relationship between happiness and owning a pet—and even studies that show that owning a dog is more beneficial than owning a cat ! Let’s say you are so intrigued by this finding that you wonder: 

What is it that makes dog owners even happier than cat owners? 

Let’s move on to Step 2 and find an answer to that question.

Writing a Hypothesis Step 2:

Formulate a strong hypothesis by answering your own question. Again, you don’t want to make things up, take unicorns into account, or repeat/ignore what has already been done. Looking at the dog-vs-cat papers your literature search returned, you see that most studies are based on self-report questionnaires on personality traits, mental health, and life satisfaction. What you don’t find is any data on actual (mental or physical) health measures, and no experiments. You therefore decide to make a bold claim come up with the carefully thought-through hypothesis that it’s maybe the lifestyle of the dog owners, which includes walking their dog several times per day, engaging in fun and healthy activities such as agility competitions, and taking them on trips, that gives them that extra boost in happiness. You could therefore answer your question in the following way:

Dog owners are happier than cat owners because of the dog-related activities they engage in.

Now you have to verify that your hypothesis fulfills the two requirements we introduced at the beginning of this resource article: falsifiability and testability . If it can’t be wrong and can’t be tested, it’s not a hypothesis. We are lucky, however, because yes, we can test whether owning a dog but not engaging in any of those activities leads to lower levels of happiness or well-being than owning a dog and playing and running around with them or taking them on trips.  

Writing a Hypothesis Step 3:

Make your predictions and define your variables. We have verified that we can test our hypothesis, but now we have to define all the relevant variables, design our experiment or data analysis, and make precise predictions. You could, for example, decide to study dog owners (not surprising at this point), let them fill in questionnaires about their lifestyle as well as their life satisfaction (as other studies did), and then compare two groups of active and inactive dog owners. Alternatively, if you want to go beyond the data that earlier studies produced and analyzed and directly manipulate the activity level of your dog owners to study the effect of that manipulation, you could invite them to your lab, select groups of participants with similar lifestyles, make them change their lifestyle (e.g., couch potato dog owners start agility classes, very active ones have to refrain from any fun activities for a certain period of time) and assess their happiness levels before and after the intervention. In both cases, your independent variable would be “ level of engagement in fun activities with dog” and your dependent variable would be happiness or well-being . 

Examples of a Good and Bad Hypothesis

Let’s look at a few examples of good and bad hypotheses to get you started.

Good Hypothesis Examples

Bad hypothesis examples, tips for writing a research hypothesis.

If you understood the distinction between a hypothesis and a prediction we made at the beginning of this article, then you will have no problem formulating your hypotheses and predictions correctly. To refresh your memory: We have to (1) look at existing evidence, (2) come up with a hypothesis, (3) make a prediction, and (4) design an experiment. For example, you could summarize your dog/happiness study like this:

(1) While research suggests that dog owners are happier than cat owners, there are no reports on what factors drive this difference. (2) We hypothesized that it is the fun activities that many dog owners (but very few cat owners) engage in with their pets that increases their happiness levels. (3) We thus predicted that preventing very active dog owners from engaging in such activities for some time and making very inactive dog owners take up such activities would lead to an increase and decrease in their overall self-ratings of happiness, respectively. (4) To test this, we invited dog owners into our lab, assessed their mental and emotional well-being through questionnaires, and then assigned them to an “active” and an “inactive” group, depending on… 

Note that you use “we hypothesize” only for your hypothesis, not for your experimental prediction, and “would” or “if – then” only for your prediction, not your hypothesis. A hypothesis that states that something “would” affect something else sounds as if you don’t have enough confidence to make a clear statement—in which case you can’t expect your readers to believe in your research either. Write in the present tense, don’t use modal verbs that express varying degrees of certainty (such as may, might, or could ), and remember that you are not drawing a conclusion while trying not to exaggerate but making a clear statement that you then, in a way, try to disprove . And if that happens, that is not something to fear but an important part of the scientific process.

Similarly, don’t use “we hypothesize” when you explain the implications of your research or make predictions in the conclusion section of your manuscript, since these are clearly not hypotheses in the true sense of the word. As we said earlier, you will find that many authors of academic articles do not seem to care too much about these rather subtle distinctions, but thinking very clearly about your own research will not only help you write better but also ensure that even that infamous Reviewer 2 will find fewer reasons to nitpick about your manuscript. 

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Now that you know how to write a strong research hypothesis for your research paper, you might be interested in our free AI proofreader , Wordvice AI, which finds and fixes errors in grammar, punctuation, and word choice in academic texts. Or if you are interested in human proofreading , check out our English editing services , including research paper editing and manuscript editing .

On the Wordvice academic resources website , you can also find many more articles and other resources that can help you with writing the other parts of your research paper , with making a research paper outline before you put everything together, or with writing an effective cover letter once you are ready to submit.

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• How to Write a Strong Hypothesis | Guide & Examples

How to Write a Strong Hypothesis | Guide & Examples

Published on 6 May 2022 by Shona McCombes .

A hypothesis is a statement that can be tested by scientific research. If you want to test a relationship between two or more variables, you need to write hypotheses before you start your experiment or data collection.

Table of contents

What is a hypothesis, developing a hypothesis (with example), hypothesis examples, frequently asked questions about writing hypotheses.

A hypothesis states your predictions about what your research will find. It is a tentative answer to your research question that has not yet been tested. For some research projects, you might have to write several hypotheses that address different aspects of your research question.

A hypothesis is not just a guess – it should be based on existing theories and knowledge. It also has to be testable, which means you can support or refute it through scientific research methods (such as experiments, observations, and statistical analysis of data).

Variables in hypotheses

Hypotheses propose a relationship between two or more variables . An independent variable is something the researcher changes or controls. A dependent variable is something the researcher observes and measures.

In this example, the independent variable is exposure to the sun – the assumed cause . The dependent variable is the level of happiness – the assumed effect .

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Step 1: ask a question.

Writing a hypothesis begins with a research question that you want to answer. The question should be focused, specific, and researchable within the constraints of your project.

Step 2: Do some preliminary research

Your initial answer to the question should be based on what is already known about the topic. Look for theories and previous studies to help you form educated assumptions about what your research will find.

At this stage, you might construct a conceptual framework to identify which variables you will study and what you think the relationships are between them. Sometimes, you’ll have to operationalise more complex constructs.

Step 3: Formulate your hypothesis

Now you should have some idea of what you expect to find. Write your initial answer to the question in a clear, concise sentence.

Step 4: Refine your hypothesis

You need to make sure your hypothesis is specific and testable. There are various ways of phrasing a hypothesis, but all the terms you use should have clear definitions, and the hypothesis should contain:

• The relevant variables
• The specific group being studied
• The predicted outcome of the experiment or analysis

Step 5: Phrase your hypothesis in three ways

To identify the variables, you can write a simple prediction in if … then form. The first part of the sentence states the independent variable and the second part states the dependent variable.

In academic research, hypotheses are more commonly phrased in terms of correlations or effects, where you directly state the predicted relationship between variables.

If you are comparing two groups, the hypothesis can state what difference you expect to find between them.

Step 6. Write a null hypothesis

If your research involves statistical hypothesis testing , you will also have to write a null hypothesis. The null hypothesis is the default position that there is no association between the variables. The null hypothesis is written as H 0 , while the alternative hypothesis is H 1 or H a .

Hypothesis testing is a formal procedure for investigating our ideas about the world using statistics. It is used by scientists to test specific predictions, called hypotheses , by calculating how likely it is that a pattern or relationship between variables could have arisen by chance.

A hypothesis is not just a guess. It should be based on existing theories and knowledge. It also has to be testable, which means you can support or refute it through scientific research methods (such as experiments, observations, and statistical analysis of data).

A research hypothesis is your proposed answer to your research question. The research hypothesis usually includes an explanation (‘ x affects y because …’).

A statistical hypothesis, on the other hand, is a mathematical statement about a population parameter. Statistical hypotheses always come in pairs: the null and alternative hypotheses. In a well-designed study , the statistical hypotheses correspond logically to the research hypothesis.

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How to Write a Hypothesis for an Essay

Last Updated: September 16, 2021

wikiHow is a “wiki,” similar to Wikipedia, which means that many of our articles are co-written by multiple authors. To create this article, volunteer authors worked to edit and improve it over time. This article has been viewed 22,067 times.

A hypothesis is an educated guess as to what will happen, given a certain set of circumstances. [1] X Research source Hypotheses are often used in science. Scientists look at a given set of circumstances or parameters and make an educated guess about how those circumstances affect something else. Then, they test that guess. Essays are often used to write up the results of these experiments. But before you ever write this type of essay, you have to choose and write out a hypothesis to test.

Narrowing Down Your Topic

• It’s easy to use the library database at your local library. Once you locate the library’s databases, you should pick out ones that are focused on science articles.
• Most libraries have some form of EBSCOhost, and if you use advanced search, you can select the databases you want, such as Science and Technology or Science Reference Center.
• Once you’ve decided on databases, you can use search terms to find what you need. Ask your librarian can help you if you’re having trouble.

• As a high school student, you’ll want to stick to more basic stuff; you can find databases geared towards your level, and your librarian should be able to point you in the right direction.
• If you’re a college student, you should be able to use most of what you find in the academic databases. You can also use your textbook to help you decide what you want to study, as well as whose theories you will base your own experiment on.
• For instance, maybe you want to study Gregor Mendel’s techniques with genetics and plants.

• It’s best to keep all of the bibliographical information together so you can find it again. Just make sure you jot down the name of the author when you begin taking notes from a source, so you know what bibliographic entry it came from.
• You should also note where you found the article or book, as well, so you can go back to it if you need to do further research.

• It is possible to be too narrow, but it is easier to expand it a bit if you need to rather than to condense it after you’ve tried to tackle too much research. If you are a younger student, such as a high school student, you may just want to repeat Mendel’s experiments to see how they work.
• If you are an older student, such as a graduate student, your work will need to be more original. You will need to put your own spin on plants and genetics. Maybe you want to study how splicing together two plants changes the genes of the plant over time.

Composing the Hypothesis

• That is, with a paper on hybrids, you might want to make one category on Mendel’s research, one for newer studies that are similar, one for splicing, and one for the type of cucumber you are using.

• To conduct the experiment, you will splice plants that manifest certain characteristics to see which produces the desired results. In this case, you are manipulating genes by picking plants for certain characteristics.
• According to Explorable, the point of an experiment is to change one variable while controlling other ones and watching for changes. [3] X Research source That is, with the cucumbers, you would need a control, such as splicing one set of cucumber plants at random, noting its characteristics, instead of choosing for a particular characteristic. Then you compare the fruit each type of plants produce.

• Also include how you plan to carry out the experiment and what you expect to happen. Because a hypothesis is a guess about what will happen, you have to spell out for your reader what you're thinking.
• Start putting it together into a formal sentence. Basically, your hypothesis is how you tell your reader in one concise sentence what you are going to do. You are boiling it down as much as possible.

• For instance, for this experiment, you could write something like, “This experiment will test the hypothesis that selecting Armenian cucumbers (scientific name Cucumis melo var. flexuosus) for crispiness and splicing those plants together will, over time, produce a crisper cucumber, and this hypothesis will be tested by selecting cucumbers for crispiness to splice with cucumbers with similar traits, along with a control group for comparing results.”
• This hypothesis is specific, it tells what you want to do, and it gives an idea of how you are going to do it.

Expert Q&A

• Essentially, to write a hypothesis, you need to pick a field and narrow down to an experiment you want to conduct. Make an educated guess about that experiment, and write it up formally for your paper. Thanks Helpful 0 Not Helpful 0
• For instance, a kid doing science project might guess that a plant will grow better if it is fed tea rather than water. It is an educated guess because the kid knows that tea has more nutrients than water, so it might help it grow faster. The kid will then test the hypothesis by performing a set of experiments over time, comparing a plant growing with just water to one growing with tea, to prove whether her hypothesis was correct or not. Thanks Helpful 0 Not Helpful 0
• Remember that you will not necessarily prove your hypothesis is correct. The point of the experiment is to see if you are right, but you may not be. The outcome of the experiment should not affect the quality of the essay one way or the other. Thanks Helpful 0 Not Helpful 0

You Might Also Like

• ↑ http://dictionary.reference.com/browse/hypothesis
• ↑ http://writingcenter.waldenu.edu/314.htm
• ↑ https://explorable.com/experimental-research

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HOW TO WRITE A HYPOTHESIS

Writing a hypothesis

Frequently, when we hear the word ‘hypothesis’, we immediately think of an investigation in the form of a science experiment. This is not surprising, as science is the subject area where we are usually first introduced to the term.

However, the term hypothesis also applies to investigations and research in many diverse areas and branches of learning, leaving us wondering how to write a hypothesis in statistics and how to write a hypothesis in sociology alongside how to write a hypothesis in a lab report.

We can find hypotheses at work in areas as wide-ranging as history, psychology, technology, engineering, literature, design, and economics. With such a vast array of uses, hypothesis writing is an essential skill for our students to develop.

What Is a Hypothesis?

A hypothesis is a proposed or predicted answer to a question. The purpose of writing a hypothesis is to follow it up by testing that answer. This test can take the form of an investigation, experiment, or writing a research paper that will ideally prove or disprove the hypothesis’s prediction.

Despite this element of the unknown, a hypothesis is not the same thing as a guess. Though the hypothesis writer typically has some uncertainty, the creation of the hypothesis is generally based on some background knowledge and research of the topic. The writer believes in the likelihood of a specific outcome, but further investigation will be required to validate or falsify the claim made in their hypothesis.

In this regard, a hypothesis is more along the lines of an ‘educated guess’ that has been based on observation and/or background knowledge.

A hypothesis should:

• Make a prediction
• Provide reasons for that prediction
• Specifies a relationship between two or more variables
• Be testable
• Be falsifiable
• Be expressed simply and concisely
• Serves as the starting point for an investigation, an experiment, or another form of testing

A COMPLETE TEACHING UNIT ON WRITING PROCEDURAL TEXTS

This HUGE BUNDLE  offers 97 PAGES of hands-on, printable, and digital media resources. Your students will be WRITING procedures with STRUCTURE, INSIGHT AND KNOWLEDGE like never before.

Hypothesis Examples for Students and Teachers

If students listen to classical music while studying, they will retain more information.

Mold growth is affected by the level of moisture in the air.

Students who sleep for longer at night retain more information at school.

Employees who work more than 40 hours per week show higher instances of clinical depression.

Time spent on social media is negatively correlated to the length of the average attention span.

People who spend time exercising regularly are less likely to develop a cardiovascular illness.

If people are shorter, then they are more likely to live longer.

What are Variables in a Hypothesis?

Variables are an essential aspect of any hypothesis. But what exactly do we mean by this term?

Variables are changeable factors or characteristics that may affect the outcome of an investigation. Things like age, weight, the height of participants, length of time, the difficulty of reading material, etc., could all be considered variables.

Usually, an investigation or experiment will focus on how different variables affect each other. So, it is vital to define the variables clearly if you are to measure the effect they have on each other accurately.

There are three main types of variables to consider in a hypothesis. These are:

• Independent Variables
• Dependent Variables

The Independent Variable

The independent variable is unaffected by any of the other variables in the hypothesis. We can think of the independent variable as the assumed cause .

The Dependent Variable

The dependent variable is affected by the other variables in the hypothesis. It is what is being tested or measured. We can think of the dependent variable as the assumed effect .

For example, let’s investigate the correlation between test scores across different age groups. The age groups will be the independent variable, and the test scores will be the dependent variable .

Now that we know what variables are let’s look at how they work in the various types of hypotheses.

Types of Hypotheses

There are many different types of hypotheses, and it is helpful to know the most common of these if the student selects the most suitable tool for their specific job.

The most frequently used types of hypotheses are:

The Simple Hypothesis

The complex hypothesis, the empirical hypothesis, the null hypothesis, the directional hypothesis, the non-directional hypothesis.

This straightforward hypothesis type predicts the relationship between an independent and dependent variable.

Example: Eating too much sugar causes weight gain.

This type of hypothesis is based on the relationship between multiple independent and/or dependent variables.

Example: Overeating sugar causes weight gain and poor cardiovascular health.

Also called a working hypothesis, an empirical hypothesis is tested through observation and experimentation. An empirical hypothesis is produced through investigation and trial and error. As a result, the empirical hypothesis may change its independent variables in the process.

Example: Exposure to sunlight helps lettuces grow faster.

This hypothesis states that there is no significant or meaningful relationship between specific variables.

Example: Exposure to sunlight does not affect the rate of a plant’s growth.

This type of hypothesis predicts the direction of an effect between variables, i.e., positive or negative.

Example: A high-quality education will result in a greater number of career opportunities.

Similar to the directional hypothesis, this type of hypothesis predicts the nature of the effect but not the direction that effect will go in.

Example: A high-quality education will affect the number of available career opportunities.

How to Write a Hypothesis : A STEP-BY-STEP GUIDE

• Ask a Question

The starting point for any hypothesis is asking a question. This is often called the research question . The research question is the student’s jumping-off point to developing their hypothesis. This question should be specific and answerable. The hypothesis will be the point where the research question is transformed into a declarative statement.

Ideally, the questions the students develop should be relational, i.e., they should look at how two or more variables relate to each other as described above. For example, what effect does sunlight have on the growth rate of lettuce?

• Research the Question

The research is an essential part of the process of developing a hypothesis. Students will need to examine the ideas and studies that are out there on the topic already. By examining the literature already out there on their topic, they can begin to refine their questions on the subject and begin to form predictions based on their studies.

Remember, a hypothesis can be defined as an ‘educated’ guess. This is the part of the process where the student educates themself on the subject before making their ‘guess.’

• Define Your Variables

By now, your students should be ready to form their preliminary hypotheses. To do this, they should first focus on defining their independent and dependent variables. Now may be an excellent opportunity to remind students that the independent variables are the only variables that they have complete control over, while dependent variables are what is tested or measured.

• Develop Your Preliminary Hypotheses

With variables defined, students can now work on a draft of their hypothesis. To do this, they can begin by examining their variables and the available data and then making a statement about the relationship between these variables. Students must brainstorm and reflect on what they expect to happen in their investigation before making a prediction upon which to base their hypothesis. It’s worth noting, too, that hypotheses are typically, though not exclusively, written in the present tense.

Students revisit the different types of hypotheses described earlier in this article. Students select three types of hypotheses and frame their preliminary hypotheses according to each criteria. Which works best? Which type is the least suitable for the student’s hypothesis?

• Finalize the Phrasing

By now, students will have made a decision on which type of hypothesis suits their needs best, and it will now be time to finalize the wording of their hypotheses. There are various ways that students can choose to frame their hypothesis, but below, we will examine the three most common ways.

The If/Then Phrasing

This is the most common type of hypothesis and perhaps the easiest to write for students. It follows a simple ‘ If x, then y ’ formula that makes a prediction that forms the basis of a subsequent investigation.

If I eat more calories, then I will gain weight.

Correlation Phrasing

Another way to phrase a hypothesis is to focus on the correlation between the variables. This typically takes the form of a statement that defines that relationship positively or negatively.

The more calories that are eaten beyond the daily recommended requirements, the greater the weight gain will be.

Comparison Phrasing

This form of phrasing is applicable when comparing two groups and focuses on the differences that the investigation is expected to reveal between those two groups.

Those who eat more calories will gain more weight than those who eat fewer calories.

Questions to ask during this process include:

• What tense is the hypothesis written in?
• Does the hypothesis contain both independent and dependent variables?
• Is the hypothesis framed using the if/then, correlation, or comparison framework (or other similar suitable structure)?
• Is the hypothesis worded clearly and concisely?
• Does the hypothesis make a prediction?
• Is the prediction specific?
• Is the hypothesis testable?
• Gather Data to Support/Disprove Your Hypothesis

If the purpose of a hypothesis is to provide a reason to pursue an investigation, then the student will need to gather related information together to fuel that investigation.

While, by definition, a hypothesis leans towards a specific outcome, the student shouldn’t worry if their investigations or experiments ultimately disprove their hypothesis. The hypothesis is the starting point; the destination is not preordained. This is the very essence of the scientific method. Students should trust the results of their investigation to speak for themselves. Either way, the outcome is valuable information.

TOP 10 TIPS FOR WRITING A STRONG HYPOTHESIS

• Begin by asking a clear and compelling question. Your hypothesis is a response to the inquiry you are eager to explore.
• Keep it simple and straightforward. Avoid using complex phrases or making multiple predictions in one hypothesis.
• Use the right format. A strong hypothesis is often written in the form of an “if-then” statement.
• Ensure that your hypothesis is testable. Your hypothesis should be something that can be verified through experimentation or observation.
• Stay objective. Your hypothesis should be based on facts and evidence, not personal opinions or prejudices.
• Examine different possibilities. Don’t limit yourself to just one hypothesis. Consider alternative explanations for your observations.
• Stay open to the possibility of being wrong. Your hypothesis is just a prediction, and it may not always be correct.
• Search for evidence to support your hypothesis. Investigate existing literature and gather data that supports your hypothesis.
• Make sure that your hypothesis is pertinent. Your hypothesis should be relevant to the question you are trying to investigate.
• Revise your hypothesis as necessary. If new evidence arises that contradicts your hypothesis, you may need to adjust it accordingly.

HYPOTHESIS TEACHING STRATEGIES AND ACTIVITIES

When teaching young scientists and writers, it’s essential to remember that the process of formulating a hypothesis is not always straightforward. It’s easy to make mistakes along the way, but with a bit of guidance, you can ensure your students avoid some of the most common pitfalls like these.

• Don’t let your students be too vague. Remind them that when formulating a hypothesis, it’s essential to be specific and avoid using overly general language. Make sure their hypothesis is clear and easy to understand.
• Being swayed by personal biases will impact their hypothesis negatively. It’s important to stay objective when formulating a hypothesis, so avoid letting personal biases or opinions get in the way.
• Not starting with a clear question is the number one stumbling block for students, so before forming a hypothesis, you need to reinforce the need for a clear understanding of the question they’re trying to answer. Start with a question that is specific and relevant.

Hypothesis Warmup Activity: First, organize students into small working groups of four or five. Then, set each group to collect a list of hypotheses. They can find these by searching on the Internet or finding examples in textbooks . When students have gathered together a suitable list of hypotheses, have them identify the independent and dependent variables in each case. They can underline each of these in different colors.

It may be helpful for students to examine each hypothesis to identify the ‘cause’ elements and the ‘effect’ elements. When students have finished, they can present their findings to the class.

Task 1: Set your students the task of coming up with an investigation-worthy question on a topic that interests them. This activity works particularly well for groups.

Task 2: Students search for existing information and theories on their topic on the Internet or in the library. They should take notes where necessary and begin to form an assumption or prediction based on their reading and research that they can investigate further.

Task 3: When working with a talking partner, can students identify which of their partner’s independent and dependent variables? If not, then one partner will need to revisit the definitions for the two types of variables as outlined earlier.

Task 4: Organize students into smaller groups and task them with presenting their hypotheses to each other. Students can then provide feedback before the final wording of each hypothesis is finalized.

Perhaps due to their short length, learning how to create a well-written hypothesis is not typically afforded much time in the curriculum.

However, though they are brief in length, they are complex enough to warrant focused learning and practice in class, particularly given their importance across many curriculum areas.

Learning how to write a hypothesis works well as a standalone writing skill. It can also form part of a more comprehensive academic or scientific writing study that focuses on how to write a research question, develop a theory, etc.

As with any text type, practice improves performance. By following the processes outlined above, students will be well on their way to writing their own hypotheses competently in no time.

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How to Write a Hypothesis: The Ultimate Guide with Examples

Hypotheses aren’t about science, experiments, and creating new theories only. While students in science classes formulate a hypothesis every second day, others from non-science fields may find it challenging to write it for an essay or a research paper.

This article is here to reveal the nature of hypothesis writing and help you learn how to write a hypothesis for essays, reports, studies, and any paper type you may need to compose.

We’ve researched all the guides, invited  our top writers  to answer all the FAQs students have on hypothesis writing, gathered hypothesis examples, and put first things first.

Yes, we are ready to make it loud and clear with our essay maker !

Table of Contents:

• Hypothesis vs. prediction
• Theory vs. hypothesis
• Hypothesis characteristics
• Thesis statement vs. hypothesis in an essay
• Main hypothesis sources
• 7 types of hypotheses you may need to write
• Ask a question
• Conduct research
• Write a null hypothesis
• Define variables
• State it using an if-then format
• What is a hypothesis in a research paper?
• How to write a hypothesis: example
• Frequently asked questions

What is a Hypothesis?

A hypothesis is an assumption you make based on existing data and knowledge, stating your predictions about what your research will find. It’s a tentative answer to your research question; it needs to be testable so you could later support or refuse it through further experiments, observations, and any other scientific research methods.

Example of a hypothesis:

Teenagers who get sex education lessons in high school will have lower rates of unplanned pregnancy than those who did not get any sex education.

Your research question here is,  “How effective is high school sex education at reducing teen pregnancies?”  and you formulate a hypothesis to check and explain in your paper.

A hypothesis always proposes a relationship between several variables. As a rule, variables are two – independent and dependent – but it’s also possible to state more variables in your hypothesis essay, to address different aspects of your research question.

• An independent variable  is the one you, as a researcher, can change or control.
• A dependent variable  is the one you, as a researcher, observe and measure based on how an independent variable changes.

In the above example, we can see that an independent variable is “sex education lessons at school” (you assume it is a cause). And a dependent variable here is “lower rates of unplanned pregnancy” (you consider it’s an effect).

Please note that there’s a difference between theory and hypothesis. Also, some guides may tell you that a hypothesis equals a  thesis statement  in essay writing, though a slight difference between these two is yet in place.

More on that below.

Hypothesis vs. Prediction

Given they both are a kind of guess, many people get a hypothesis and a prediction confused. But while a difference is slight, it’s yet critical:

• A hypothesis  explains  why something happens based on  scientific methods  (testing, experiments, data analysis, etc.).
• A prediction  suggests  that something will happen based on  observations .

You write a hypothesis using a statement with variables, while a prediction consists of “if-then” schemes stating about future happenings.

We can also say that a prediction is something you expect to happen if your hypothesis statement is true.

Theory vs. Hypothesis

• A hypothesis states a  suggested  explanation of a phenomenon, which you’ll later support or refuse through testing and other scientific methods.
• A theory is an  already tested , well-substantiated explanation backed by evidence.

You write a hypothesis using a statement with variables, while a theory represents a phenomenon that is already widely accepted and supported by data.

Examples of theories include Einstein’s theory of relativity, the Big Bang theory, Charles Darwin’s theory of evolution, and many others.

For your hypothesis to become a theory, you need to test all the aspects under various circumstances and prove it with well-substantiated facts. You can also use theories to make predictions about something unexplained and then turn those predictions into hypotheses to test and support (or refuse).

It’s worth noting that testings don’t stop once a hypothesis becomes a theory: Science is ongoing, and any theory can become disproved one day.

Hypothesis Characteristics

And now it’s high time to reveal the characteristics of your statement to become a reasonable hypothesis.

They are five:

• A cause-effect relationship between variables . When writing a hypothesis, make sure your one variable causes another one to change (or not change.) There should always be a cause-effect relationship between them.
• Testable nature.  Formulate a hypothesis that you can  test  to support or refuse. You should be able to conduct experiments and control your thesis when working on it.
• Precise and accurate variables.  Your hypothesis’s independent and dependent variables need to be specific and clear for the audience to understand.
• Explained in simple language.   Research papers  and academic writing, in general, are often challenging to understand for an average reader, so do your best to write a hypothesis so there would be no confusion or ambiguity.
• Ethical.  We can test many things, but there’s always a question about  what  we should test or make a subject to experiments. Avoid questionable or taboo topics when thinking about your hypothesis outline.

Thesis Statement vs. Hypothesis in an Essay

When looking for information on writing a hypothesis essay, you can find guides telling that it’s the same with writing a thesis statement for your  argumentative essay . This notion is not entirely true, and there’s still a slight difference between these two:

• A thesis statement is a sentence or two in your essay introduction that summarizes a central claim you’ll  discuss and prove  in the essay body. You’ll use arguments, evidence, and examples for that. 
• A hypothesis is a one-sentence prediction based on the relationships between reliables that you’ll  test   and then  prove or disprove  in the essay body. You’ll use experiments, observation, and quantitative research for that.

Writing a research study should have a thesis statement; if your research intends to prove/disprove something, it will also contain a hypothesis statement.

Feel free to try our  online thesis statement generator  to get a better idea of writing strong thesis statements for your essays.

Main Hypothesis Sources

Once they ask you to write a hypothesis essay, it would be great to have some sources for inspiration at hand, wouldn’t it?

Where to go for  creative ideas ? Where to research hypothesis and come up with new statements for your essay? What sources do science students use?

The primary hypothesis sources are four:

• Scientific theories that already exist
• Some general patterns affecting our thinking process
• Analogies between different phenomena we observe
• The previous knowledge and observations from studies and our experience

Depending on the niche and type of hypothesis you need to cover, you’ll use corresponding sources for research and further hypothesis  outline .

Below you’ll learn what types of hypotheses exist and how to write a hypothesis statement so it would sound scientific.

7 Types of Hypotheses You May Need to Write

So many sources, so many hypothesis classifications they offer. Some specify eight, ten, and even 13  types of hypotheses, depending on the factors like the number of variables you use and the experiment stage you’re in. Some insist that only two significant kinds of hypotheses exist: alternative and null; others call them directional and non-directional hypotheses, respectively.

Let’s put things straight and explain the types of hypotheses you may need to write in essays . They are seven, with examples for you to get a better idea of “who is who,” as they say.

1) Simple hypothesis

It’s the most common type of hypothesis to use in college papers, predicting the direct relationship between two variables in your experiment: a single dependent and a single independent one.

How to write a simple hypothesis? Use an “if-then” format.

For example:

• Everyday smoking leads to lung cancer.  ( If  you smoke every day,  then  you’ll get lung cancer.)
• Covering wounds with a bandage heals with fewer scars.  ( If  you bandage an injury,  then  it will heal with less scarring.)

2) Complex hypothesis

This one also predicts the relationship between variables but has more than two dependent and independent variables to check for supporting or refusing.

• Overweight people who eat junk food have higher chances of getting excessive cholesterol and heart disease.  (Two independent variables are  extra weight  and  junk food consumption ; two dependent variables are  heart disease  and  high cholesterol level .)
• The higher illiteracy in a society, the higher is poverty and crime rate.  (One independent variable is higher  illiteracy , and two dependent variables are higher  poverty  and higher  crime rate .)

3) Null hypothesis

How to write a null hypothesis? It’s the default position stating there’s no relationship between variables, i.e., there will be no difference in the experiment’s results. 

Scientists use null hypotheses to disapprove or reaffirm given statements.

• A person’s productivity doesn’t suffer from getting six instead of eight hours of sleep.
• All daisies are equal in the number of their petals.
• Sex education in high school doesn’t affect unplanned pregnancy rates.

4) Alternative hypothesis

When searching for information on how to write a hypothesis online, you might see queries like “how to write a null and alternative hypothesis.” That’s because alternative hypothesis statements come in place when someone tries to  disprove  a null hypothesis, so these two go hand in hand.

In other words, an alternative hypothesis  directly contradicts  a null one.

Also, an alternative hypothesis is one you may want to develop when the experiment on your initial statement doesn’t bring any result.

• H0 (a null hypothesis): Light color does not affect plant growth.
• H1 (an alternative hypothesis): Light color affects plant growth.
• H0: Cats have no preference for food based on shape.
• H1: Cats prefer round kibbles to other food shapes.

5) Logical hypothesis

This one is a hypothesis you can verify logically, though there’s little to no substantial evidence for it. Here you use reasoning and logical connections instead of proven facts, statistics, or background research.

Logical hypotheses remain assumptions until you put them to the test and support/refuse them after experiments.

• Dogs won’t survive without water.  (Here, you make an assumption based on the fact humans can’t live without water, so dogs, as mammals, won’t do that, either.)
• Creatures from Mars won’t breathe in the Earth’s atmosphere.  (Here, you assume that they won’t because we humans can’t breathe on Mars.)

6) Empirical hypothesis

In plain English, it’s a currently-tested hypothesis that can yet be changed or adjusted according to the results of experiments. It’s a working hypothesis that’s yet to confirm or refuse:

Empirical hypotheses are those going through tests, trials, or errors via observation and experiments right now and can be changed later around the independent variables. As a rule, it’s the opposite of a logical hypothesis.

• Women taking vitamin E grow hair faster than those taking vitamin K.
• Mushrooms grow faster at 22 degrees Celsius than 27 degrees Celsius.

7) Statistical hypothesis

This one is a hypothesis you can test and verify statistically based on data and quantitative research methods.

How to write a statistical hypothesis?

Statistical hypotheses have quantifiable variables and are usually about the nature of a population. It comes in handy when it’s impossible to test or survey every single person in a group. To write such a hypothesis, you’ll need to state the data about your topic using a portion of people.

• 35% of the poor in the USA are illiterate.
• 60% of people talking on the phone while driving have been in at least one car accident.
• 56% of marriages end in divorce.

How to Write a Hypothesis: 5 Steps

First and foremost, it’s worth mentioning that hypothesis writing is the third step of the scientific method scholars, researchers, and science students use to test theories, answer questions, and solve problems.

The steps are six, and they are as follows:

• Observation:  Decide on an issue to solve or a phenomenon to explain. 
• Question:  Develop a research question you’d like to check.
• Hypothesis (we are here!):  Formulate a hypothesis that answers your question and that you can test.
• Prediction:  Determine the experiment’s outcome based on your hypothesis.
• Test:  Do your experiments to test your prediction.
• Analyze:  Review the results to see if your hypothesis was correct. If it wasn’t, you could revise it by formulating another one and going through the whole process again.

In academic writing, hypotheses come as something relating to thesis statements: It’s a sentence or two summarizing a central claim you’ll discuss and prove in your essay.

It stands to reason that hypothesis writing is more common for STEM disciplines like math, chemistry, biology, physics, or economics. Here’s how to craft it, step by step:

1) Ask a Question

This stage is about choosing an  argumentative topic for your essay . Except as assigned by a teacher or a thesis tutor, you can start with an issue of your interest, so your curiosity and questions on it come naturally.

Why is it the way it is?

Why does it happen the way it goes?

What causes this factor you see around?

Your question needs to be  clear ,  specific , and  manageable  so you can research it, test it, and analyze the results. Also, ensure it’s not too broad so you can focus on its particular aspect to formulate your hypothesis.

For example:   How does eating apples affect human dental health?

2) Conduct Research

Now you’ll need to check and collect some information on your question to understand if it’s possible to formulate a research hypothesis. It’s so-called initial research to find an answer to your question.

This stage is not about proving or disproving your hypothesis. Here you’ll collect facts, theories, past studies, and any other information that will help prove or disprove it so that you can make an apparent assumption: Based on the gathered information, you’ll be able to make a logical guess.

Depending on your question, this initial research can  take some time  from you. You may need to read a few books on the topic, find and compare some scientific materials, etc. Or, it may be enough to perform a quick web search to find the answer.

3) Write a Null Hypothesis

To ease the process of hypothesis writing, start with a null hypothesis. As you already know, it’s the default position stating no relationship between variables. (And that’s why it’s so easy to formulate.)

So, take your initial question and write it as a negative statement. In our example with eating apples and dental health, the null hypothesis would sound like that:

Eating apples do not affect a human’s dental health.

(Which means your teeth condition will be the same, whether you eat apples or not.)

4) Define Variables

And now, for your hypothesis to become testable so you can do experiments, make predictions, and analyze the results, think of dependent and independent variables for it.

As you already know, independent variables are the factors you, as a researcher, can control during experiments to check the hypothesis. 

Example:   Eating one apple a day will positively affect a human’s dental health.

“One apple” is the independent variable, and “dental health” is the dependent variable here.

You’ll come up with variables based on your initial research. With some facts and studies already in place, you can predict how your experiment may go and what its results may be. Use this knowledge to shape variables into a clear and concise hypothesis.

And remember:

The way you’ll frame a hypothesis into one sentence depends on a few factors: the type of your project and the type of hypothesis you want to use. 

Simple hypotheses are most common for student research papers , so we use them as examples here. With that in mind, the final stage of hypothesis writing comes:

5) State It Using an If-Then Format

To formulate a hypothesis the best way possible, try framing it with an “if-then” format. Like this:

If a human eats one apple per day, then he gets healthier teeth.

This format becomes tricky when working with complex hypotheses with multiple variables, but it’s reliable when expressing the cause-and-effect relationship. 

The “if-then” format allows you to refine a hypothesis and ensure its final version:

• is clear, specific, and testable;
• has relevant variables;
• identifies the relationship between variables;
• suggests a predicted result of the experiment.

Another way to check if you’ve shaped a hypothesis properly is using the “PICOT” model, best explained via  visual examples . According to this model, a hypothesis should have five components:

P –  population: the specific group or individual of your research

I –  interest: the primary concern of your study

C –  comparison: the leading alternative group

O –  outcome: the expected result

T – time: the length of your experimen t

Always write a hypothesis in  the present tense  because it refers to research that’s currently being conducted.

What is a Hypothesis in a Research Paper?

A hypothesis in a research paper is a statement demonstrating a prediction you believe may happen based on research, evidence, and experimentation.

Often used and associated with science, hypotheses are assumptions (or guesses) for researchers and scholars to prove or disprove via tests and experiments. And they later write a hypothesis essay to analyze and report the experiments’ results to the scientific community.

When writing a hypothesis for a research paper, you should still describe an experiment to prove or disprove it. However, hypothesis essays don’t necessarily have to be on STEM disciplines and tests taken in a lab:

• You can  write a book critique  and state a hypothesis on its or its author’s impact on literature. 
• Or, your hypothesis essay can be about how demographics change a country’s language.
• Or, you’ll  write an autobiography  with a focus on the hypothesis that one particular event influenced your further deeds. 

In such essays, you won’t spend hours in labs to prove that your hypothesis is true; you’ll do that through research, arguments, data, interviews, or previous studies.

Is a thesis statement a hypothesis?

As we already mentioned, there’s a slight difference between these two. While  thesis statements  in essays are about  summarizing  a central claim you’ll discuss,  hypotheses  are about  predictions  or  assumptions  you’ll prove (or disprove) in the essay body.

You don’t have to prove that your hypothesis is correct. The point is to research, test, and experiment to see if you’re right. Even if your hypothesis appears incorrect in  conclusion , it doesn’t mean the quality of your essay is poor.

How to Write a Hypothesis: Example

And now, let’s go to even more hypothesis examples for you to understand the nature of this writing better.

Here goes another example of a hypothesis:

Frequently Asked Questions

What is a hypothesis in an essay.

A hypothesis in an essay is a statement demonstrating a prediction you believe may happen based on research, evidence, and experimentation. As a rule, it predicts the relationship between a few variables; and you can prove or disprove it by the end of your tests and experiments on it.

How long is a hypothesis?

A hypothesis is one-sentence long. It should be clear, direct, and testable through experimentation, predicting a possible outcome.

How to write a hypothesis statement?

First of all, you need to state a problem you’re trying to solve, do some initial research on it to learn the background and predict an outcome, and then think of both dependent and independent variables for your hypothesis. For that, research or brainstorm ideas for your stated problem’s solution. Finally, write your hypothesis as an “if-then” statement, using your variables.

How to write a null hypothesis?

A null hypothesis is the default position stating no relationship between variables. To write it, you need to assume an experiment has no effect regardless of variables; use denying. 

For example, you want to learn whether teens are better at math than adults. In this case, your null hypothesis will be, “ Age does not affect math ability.”

How to write an alternative hypothesis?

An alternative hypothesis directly contradicts   a null one, trying to disprove it. To write it, you need to assume there’s enough evidence to reject the null hypothesis; but never state your claim is already proven true or false.

In contrast with a null hypothesis, typically marked as H0, an alternative one gets an H1 mark. For example:

H0: If I put Mentos into a Coke bottle, there will be no reaction.

H1: If I put Mentos into a Coke bottle, there will be a big explosion.

How to write a simple hypothesis?

A simple hypothesis is the most common one to use in college papers. It predicts the direct relationship between two variables — one dependent and one independent, — so write a simple hypothesis with an “if-then” format.

For example: 

If a postpartum woman has low hemoglobin, then she gets higher risk of infection.

A statistical hypothesis claims the value of a single population characteristic or relationship between several population characteristics. To write it, you first need to specify null and alternative hypotheses, set the significance level, calculate the statistics, and draw a conclusion. Ensure that your variables are quantifiable. For example: 

A population mean is equal to 10.

How to write a hypothesis for a lab report?

To write a hypothesis for a lab report, you should state the issue, predict its outcome based on tests and experiments, define the variables, and formulate a hypothesis as an if-then statement. For example:

If one puts Mentos in a bottle with Coke, there will be an explosion.

How to write a hypothesis for a research paper?

• Decide on a question/problem you want to check/solve.
• Conduct initial research to collect as much background information and observation about your topic as you can.
• Evaluate this information to assume possible causes and possible explanations.
• Define variables you’ll use to confirm or disprove your hypothesis through experimentation.
• Write down a one-sentence hypothesis using the present tense.

Now that you know how to write a hypothesis, it’s high time to give it a try:

• Address your curiosity.
• Ask questions.
• Conduct some initial research.
• Come up with a type of hypothesis that fits your expectations most.

Think of variables for your hypothesis, and ensure it’s clear, concise, and measurable (testable). Then write it in the present tense — and you’ve got it!

Any questions left? Don’t hesitate to write in the comments (yes, we read them and reply!) or ask  Bid4Papers writers  directly!

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How to Write a Great Hypothesis

Hypothesis Definition, Format, Examples, and Tips

Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

Amy Morin, LCSW, is a psychotherapist and international bestselling author. Her books, including "13 Things Mentally Strong People Don't Do," have been translated into more than 40 languages. Her TEDx talk,  "The Secret of Becoming Mentally Strong," is one of the most viewed talks of all time.

Verywell / Alex Dos Diaz

• The Scientific Method

Hypothesis Format

Falsifiability of a hypothesis.

• Operationalization

Hypothesis Types

Hypotheses examples.

• Collecting Data

A hypothesis is a tentative statement about the relationship between two or more variables. It is a specific, testable prediction about what you expect to happen in a study. It is a preliminary answer to your question that helps guide the research process.

Consider a study designed to examine the relationship between sleep deprivation and test performance. The hypothesis might be: "This study is designed to assess the hypothesis that sleep-deprived people will perform worse on a test than individuals who are not sleep-deprived."

At a Glance

A hypothesis is crucial to scientific research because it offers a clear direction for what the researchers are looking to find. This allows them to design experiments to test their predictions and add to our scientific knowledge about the world. This article explores how a hypothesis is used in psychology research, how to write a good hypothesis, and the different types of hypotheses you might use.

The Hypothesis in the Scientific Method

In the scientific method , whether it involves research in psychology, biology, or some other area, a hypothesis represents what the researchers think will happen in an experiment. The scientific method involves the following steps:

• Forming a question
• Performing background research
• Creating a hypothesis
• Designing an experiment
• Collecting data
• Analyzing the results
• Drawing conclusions
• Communicating the results

The hypothesis is a prediction, but it involves more than a guess. Most of the time, the hypothesis begins with a question which is then explored through background research. At this point, researchers then begin to develop a testable hypothesis.

Unless you are creating an exploratory study, your hypothesis should always explain what you  expect  to happen.

In a study exploring the effects of a particular drug, the hypothesis might be that researchers expect the drug to have some type of effect on the symptoms of a specific illness. In psychology, the hypothesis might focus on how a certain aspect of the environment might influence a particular behavior.

Remember, a hypothesis does not have to be correct. While the hypothesis predicts what the researchers expect to see, the goal of the research is to determine whether this guess is right or wrong. When conducting an experiment, researchers might explore numerous factors to determine which ones might contribute to the ultimate outcome.

In many cases, researchers may find that the results of an experiment  do not  support the original hypothesis. When writing up these results, the researchers might suggest other options that should be explored in future studies.

In many cases, researchers might draw a hypothesis from a specific theory or build on previous research. For example, prior research has shown that stress can impact the immune system. So a researcher might hypothesize: "People with high-stress levels will be more likely to contract a common cold after being exposed to the virus than people who have low-stress levels."

In other instances, researchers might look at commonly held beliefs or folk wisdom. "Birds of a feather flock together" is one example of folk adage that a psychologist might try to investigate. The researcher might pose a specific hypothesis that "People tend to select romantic partners who are similar to them in interests and educational level."

Elements of a Good Hypothesis

So how do you write a good hypothesis? When trying to come up with a hypothesis for your research or experiments, ask yourself the following questions:

• Is your hypothesis based on your research on a topic?
• Can your hypothesis be tested?
• Does your hypothesis include independent and dependent variables?

Before you come up with a specific hypothesis, spend some time doing background research. Once you have completed a literature review, start thinking about potential questions you still have. Pay attention to the discussion section in the  journal articles you read . Many authors will suggest questions that still need to be explored.

How to Formulate a Good Hypothesis

To form a hypothesis, you should take these steps:

• Collect as many observations about a topic or problem as you can.
• Evaluate these observations and look for possible causes of the problem.
• Create a list of possible explanations that you might want to explore.
• After you have developed some possible hypotheses, think of ways that you could confirm or disprove each hypothesis through experimentation. This is known as falsifiability.

In the scientific method ,  falsifiability is an important part of any valid hypothesis. In order to test a claim scientifically, it must be possible that the claim could be proven false.

Students sometimes confuse the idea of falsifiability with the idea that it means that something is false, which is not the case. What falsifiability means is that  if  something was false, then it is possible to demonstrate that it is false.

One of the hallmarks of pseudoscience is that it makes claims that cannot be refuted or proven false.

The Importance of Operational Definitions

A variable is a factor or element that can be changed and manipulated in ways that are observable and measurable. However, the researcher must also define how the variable will be manipulated and measured in the study.

Operational definitions are specific definitions for all relevant factors in a study. This process helps make vague or ambiguous concepts detailed and measurable.

For example, a researcher might operationally define the variable " test anxiety " as the results of a self-report measure of anxiety experienced during an exam. A "study habits" variable might be defined by the amount of studying that actually occurs as measured by time.

These precise descriptions are important because many things can be measured in various ways. Clearly defining these variables and how they are measured helps ensure that other researchers can replicate your results.

Replicability

One of the basic principles of any type of scientific research is that the results must be replicable.

Replication means repeating an experiment in the same way to produce the same results. By clearly detailing the specifics of how the variables were measured and manipulated, other researchers can better understand the results and repeat the study if needed.

Some variables are more difficult than others to define. For example, how would you operationally define a variable such as aggression ? For obvious ethical reasons, researchers cannot create a situation in which a person behaves aggressively toward others.

To measure this variable, the researcher must devise a measurement that assesses aggressive behavior without harming others. The researcher might utilize a simulated task to measure aggressiveness in this situation.

Hypothesis Checklist

• Does your hypothesis focus on something that you can actually test?
• Does your hypothesis include both an independent and dependent variable?
• Can you manipulate the variables?
• Can your hypothesis be tested without violating ethical standards?

The hypothesis you use will depend on what you are investigating and hoping to find. Some of the main types of hypotheses that you might use include:

• Simple hypothesis : This type of hypothesis suggests there is a relationship between one independent variable and one dependent variable.
• Complex hypothesis : This type suggests a relationship between three or more variables, such as two independent and dependent variables.
• Null hypothesis : This hypothesis suggests no relationship exists between two or more variables.
• Alternative hypothesis : This hypothesis states the opposite of the null hypothesis.
• Statistical hypothesis : This hypothesis uses statistical analysis to evaluate a representative population sample and then generalizes the findings to the larger group.
• Logical hypothesis : This hypothesis assumes a relationship between variables without collecting data or evidence.

A hypothesis often follows a basic format of "If {this happens} then {this will happen}." One way to structure your hypothesis is to describe what will happen to the  dependent variable  if you change the  independent variable .

The basic format might be: "If {these changes are made to a certain independent variable}, then we will observe {a change in a specific dependent variable}."

A few examples of simple hypotheses:

• "Students who eat breakfast will perform better on a math exam than students who do not eat breakfast."
• "Students who experience test anxiety before an English exam will get lower scores than students who do not experience test anxiety."​
• "Motorists who talk on the phone while driving will be more likely to make errors on a driving course than those who do not talk on the phone."
• "Children who receive a new reading intervention will have higher reading scores than students who do not receive the intervention."

Examples of a complex hypothesis include:

• "People with high-sugar diets and sedentary activity levels are more likely to develop depression."
• "Younger people who are regularly exposed to green, outdoor areas have better subjective well-being than older adults who have limited exposure to green spaces."

Examples of a null hypothesis include:

• "There is no difference in anxiety levels between people who take St. John's wort supplements and those who do not."
• "There is no difference in scores on a memory recall task between children and adults."
• "There is no difference in aggression levels between children who play first-person shooter games and those who do not."

Examples of an alternative hypothesis:

• "People who take St. John's wort supplements will have less anxiety than those who do not."
• "Adults will perform better on a memory task than children."
• "Children who play first-person shooter games will show higher levels of aggression than children who do not." 

Collecting Data on Your Hypothesis

Once a researcher has formed a testable hypothesis, the next step is to select a research design and start collecting data. The research method depends largely on exactly what they are studying. There are two basic types of research methods: descriptive research and experimental research.

Descriptive Research Methods

Descriptive research such as  case studies ,  naturalistic observations , and surveys are often used when  conducting an experiment is difficult or impossible. These methods are best used to describe different aspects of a behavior or psychological phenomenon.

Once a researcher has collected data using descriptive methods, a  correlational study  can examine how the variables are related. This research method might be used to investigate a hypothesis that is difficult to test experimentally.

Experimental Research Methods

Experimental methods  are used to demonstrate causal relationships between variables. In an experiment, the researcher systematically manipulates a variable of interest (known as the independent variable) and measures the effect on another variable (known as the dependent variable).

Unlike correlational studies, which can only be used to determine if there is a relationship between two variables, experimental methods can be used to determine the actual nature of the relationship—whether changes in one variable actually  cause  another to change.

The hypothesis is a critical part of any scientific exploration. It represents what researchers expect to find in a study or experiment. In situations where the hypothesis is unsupported by the research, the research still has value. Such research helps us better understand how different aspects of the natural world relate to one another. It also helps us develop new hypotheses that can then be tested in the future.

Thompson WH, Skau S. On the scope of scientific hypotheses .  R Soc Open Sci . 2023;10(8):230607. doi:10.1098/rsos.230607

Taran S, Adhikari NKJ, Fan E. Falsifiability in medicine: what clinicians can learn from Karl Popper [published correction appears in Intensive Care Med. 2021 Jun 17;:].  Intensive Care Med . 2021;47(9):1054-1056. doi:10.1007/s00134-021-06432-z

Eyler AA. Research Methods for Public Health . 1st ed. Springer Publishing Company; 2020. doi:10.1891/9780826182067.0004

Nosek BA, Errington TM. What is replication ?  PLoS Biol . 2020;18(3):e3000691. doi:10.1371/journal.pbio.3000691

Aggarwal R, Ranganathan P. Study designs: Part 2 - Descriptive studies .  Perspect Clin Res . 2019;10(1):34-36. doi:10.4103/picr.PICR_154_18

Nevid J. Psychology: Concepts and Applications. Wadworth, 2013.

By Kendra Cherry, MSEd Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

How to Develop a Good Research Hypothesis

The story of a research study begins by asking a question. Researchers all around the globe are asking curious questions and formulating research hypothesis. However, whether the research study provides an effective conclusion depends on how well one develops a good research hypothesis. Research hypothesis examples could help researchers get an idea as to how to write a good research hypothesis.

This blog will help you understand what is a research hypothesis, its characteristics and, how to formulate a research hypothesis

Table of Contents

What is Hypothesis?

Hypothesis is an assumption or an idea proposed for the sake of argument so that it can be tested. It is a precise, testable statement of what the researchers predict will be outcome of the study.  Hypothesis usually involves proposing a relationship between two variables: the independent variable (what the researchers change) and the dependent variable (what the research measures).

What is a Research Hypothesis?

Research hypothesis is a statement that introduces a research question and proposes an expected result. It is an integral part of the scientific method that forms the basis of scientific experiments. Therefore, you need to be careful and thorough when building your research hypothesis. A minor flaw in the construction of your hypothesis could have an adverse effect on your experiment. In research, there is a convention that the hypothesis is written in two forms, the null hypothesis, and the alternative hypothesis (called the experimental hypothesis when the method of investigation is an experiment).

Characteristics of a Good Research Hypothesis

As the hypothesis is specific, there is a testable prediction about what you expect to happen in a study. You may consider drawing hypothesis from previously published research based on the theory.

A good research hypothesis involves more effort than just a guess. In particular, your hypothesis may begin with a question that could be further explored through background research.

To help you formulate a promising research hypothesis, you should ask yourself the following questions:

• Is the language clear and focused?
• What is the relationship between your hypothesis and your research topic?
• Is your hypothesis testable? If yes, then how?
• What are the possible explanations that you might want to explore?
• Does your hypothesis include both an independent and dependent variable?
• Can you manipulate your variables without hampering the ethical standards?
• Does your research predict the relationship and outcome?
• Is your research simple and concise (avoids wordiness)?
• Is it clear with no ambiguity or assumptions about the readers’ knowledge
• Is your research observable and testable results?
• Is it relevant and specific to the research question or problem?

The questions listed above can be used as a checklist to make sure your hypothesis is based on a solid foundation. Furthermore, it can help you identify weaknesses in your hypothesis and revise it if necessary.

Source: Educational Hub

How to formulate a research hypothesis.

A testable hypothesis is not a simple statement. It is rather an intricate statement that needs to offer a clear introduction to a scientific experiment, its intentions, and the possible outcomes. However, there are some important things to consider when building a compelling hypothesis.

1. State the problem that you are trying to solve.

Make sure that the hypothesis clearly defines the topic and the focus of the experiment.

2. Try to write the hypothesis as an if-then statement.

Follow this template: If a specific action is taken, then a certain outcome is expected.

3. Define the variables

Independent variables are the ones that are manipulated, controlled, or changed. Independent variables are isolated from other factors of the study.

Dependent variables , as the name suggests are dependent on other factors of the study. They are influenced by the change in independent variable.

4. Scrutinize the hypothesis

Evaluate assumptions, predictions, and evidence rigorously to refine your understanding.

Types of Research Hypothesis

The types of research hypothesis are stated below:

1. Simple Hypothesis

It predicts the relationship between a single dependent variable and a single independent variable.

2. Complex Hypothesis

It predicts the relationship between two or more independent and dependent variables.

3. Directional Hypothesis

It specifies the expected direction to be followed to determine the relationship between variables and is derived from theory. Furthermore, it implies the researcher’s intellectual commitment to a particular outcome.

4. Non-directional Hypothesis

It does not predict the exact direction or nature of the relationship between the two variables. The non-directional hypothesis is used when there is no theory involved or when findings contradict previous research.

5. Associative and Causal Hypothesis

The associative hypothesis defines interdependency between variables. A change in one variable results in the change of the other variable. On the other hand, the causal hypothesis proposes an effect on the dependent due to manipulation of the independent variable.

6. Null Hypothesis

Null hypothesis states a negative statement to support the researcher’s findings that there is no relationship between two variables. There will be no changes in the dependent variable due the manipulation of the independent variable. Furthermore, it states results are due to chance and are not significant in terms of supporting the idea being investigated.

7. Alternative Hypothesis

It states that there is a relationship between the two variables of the study and that the results are significant to the research topic. An experimental hypothesis predicts what changes will take place in the dependent variable when the independent variable is manipulated. Also, it states that the results are not due to chance and that they are significant in terms of supporting the theory being investigated.

Research Hypothesis Examples of Independent and Dependent Variables

Research Hypothesis Example 1 The greater number of coal plants in a region (independent variable) increases water pollution (dependent variable). If you change the independent variable (building more coal factories), it will change the dependent variable (amount of water pollution).

Research Hypothesis Example 2 What is the effect of diet or regular soda (independent variable) on blood sugar levels (dependent variable)? If you change the independent variable (the type of soda you consume), it will change the dependent variable (blood sugar levels)

You should not ignore the importance of the above steps. The validity of your experiment and its results rely on a robust testable hypothesis. Developing a strong testable hypothesis has few advantages, it compels us to think intensely and specifically about the outcomes of a study. Consequently, it enables us to understand the implication of the question and the different variables involved in the study. Furthermore, it helps us to make precise predictions based on prior research. Hence, forming a hypothesis would be of great value to the research. Here are some good examples of testable hypotheses.

More importantly, you need to build a robust testable research hypothesis for your scientific experiments. A testable hypothesis is a hypothesis that can be proved or disproved as a result of experimentation.

Importance of a Testable Hypothesis

To devise and perform an experiment using scientific method, you need to make sure that your hypothesis is testable. To be considered testable, some essential criteria must be met:

• There must be a possibility to prove that the hypothesis is true.
• There must be a possibility to prove that the hypothesis is false.
• The results of the hypothesis must be reproducible.

Without these criteria, the hypothesis and the results will be vague. As a result, the experiment will not prove or disprove anything significant.

What are your experiences with building hypotheses for scientific experiments? What challenges did you face? How did you overcome these challenges? Please share your thoughts with us in the comments section.

Frequently Asked Questions

The steps to write a research hypothesis are: 1. Stating the problem: Ensure that the hypothesis defines the research problem 2. Writing a hypothesis as an 'if-then' statement: Include the action and the expected outcome of your study by following a ‘if-then’ structure. 3. Defining the variables: Define the variables as Dependent or Independent based on their dependency to other factors. 4. Scrutinizing the hypothesis: Identify the type of your hypothesis

Hypothesis testing is a statistical tool which is used to make inferences about a population data to draw conclusions for a particular hypothesis.

Hypothesis in statistics is a formal statement about the nature of a population within a structured framework of a statistical model. It is used to test an existing hypothesis by studying a population.

Research hypothesis is a statement that introduces a research question and proposes an expected result. It forms the basis of scientific experiments.

The different types of hypothesis in research are: • Null hypothesis: Null hypothesis is a negative statement to support the researcher’s findings that there is no relationship between two variables. • Alternate hypothesis: Alternate hypothesis predicts the relationship between the two variables of the study. • Directional hypothesis: Directional hypothesis specifies the expected direction to be followed to determine the relationship between variables. • Non-directional hypothesis: Non-directional hypothesis does not predict the exact direction or nature of the relationship between the two variables. • Simple hypothesis: Simple hypothesis predicts the relationship between a single dependent variable and a single independent variable. • Complex hypothesis: Complex hypothesis predicts the relationship between two or more independent and dependent variables. • Associative and casual hypothesis: Associative and casual hypothesis predicts the relationship between two or more independent and dependent variables. • Empirical hypothesis: Empirical hypothesis can be tested via experiments and observation. • Statistical hypothesis: A statistical hypothesis utilizes statistical models to draw conclusions about broader populations.

Wow! You really simplified your explanation that even dummies would find it easy to comprehend. Thank you so much.

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I enjoy reading the post. Hypotheses are actually an intrinsic part in a study. It bridges the research question and the methodology of the study.

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It very interesting to read the topic, can you guide me any specific example of hypothesis process establish throw the Demand and supply of the specific product in market

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What is and How to Write a Good Hypothesis in Research?

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• 315.3K views

Table of Contents

One of the most important aspects of conducting research is constructing a strong hypothesis. But what makes a hypothesis in research effective? In this article, we’ll look at the difference between a hypothesis and a research question, as well as the elements of a good hypothesis in research. We’ll also include some examples of effective hypotheses, and what pitfalls to avoid.

What is a Hypothesis in Research?

Simply put, a hypothesis is a research question that also includes the predicted or expected result of the research. Without a hypothesis, there can be no basis for a scientific or research experiment. As such, it is critical that you carefully construct your hypothesis by being deliberate and thorough, even before you set pen to paper. Unless your hypothesis is clearly and carefully constructed, any flaw can have an adverse, and even grave, effect on the quality of your experiment and its subsequent results.

Research Question vs Hypothesis

It’s easy to confuse research questions with hypotheses, and vice versa. While they’re both critical to the Scientific Method, they have very specific differences. Primarily, a research question, just like a hypothesis, is focused and concise. But a hypothesis includes a prediction based on the proposed research, and is designed to forecast the relationship of and between two (or more) variables. Research questions are open-ended, and invite debate and discussion, while hypotheses are closed, e.g. “The relationship between A and B will be C.”

A hypothesis is generally used if your research topic is fairly well established, and you are relatively certain about the relationship between the variables that will be presented in your research. Since a hypothesis is ideally suited for experimental studies, it will, by its very existence, affect the design of your experiment. The research question is typically used for new topics that have not yet been researched extensively. Here, the relationship between different variables is less known. There is no prediction made, but there may be variables explored. The research question can be casual in nature, simply trying to understand if a relationship even exists, descriptive or comparative.

How to Write Hypothesis in Research

Writing an effective hypothesis starts before you even begin to type. Like any task, preparation is key, so you start first by conducting research yourself, and reading all you can about the topic that you plan to research. From there, you’ll gain the knowledge you need to understand where your focus within the topic will lie.

Remember that a hypothesis is a prediction of the relationship that exists between two or more variables. Your job is to write a hypothesis, and design the research, to “prove” whether or not your prediction is correct. A common pitfall is to use judgments that are subjective and inappropriate for the construction of a hypothesis. It’s important to keep the focus and language of your hypothesis objective.

An effective hypothesis in research is clearly and concisely written, and any terms or definitions clarified and defined. Specific language must also be used to avoid any generalities or assumptions.

Use the following points as a checklist to evaluate the effectiveness of your research hypothesis:

• Predicts the relationship and outcome
• Simple and concise – avoid wordiness
• Clear with no ambiguity or assumptions about the readers’ knowledge
• Observable and testable results
• Relevant and specific to the research question or problem

Research Hypothesis Example

Perhaps the best way to evaluate whether or not your hypothesis is effective is to compare it to those of your colleagues in the field. There is no need to reinvent the wheel when it comes to writing a powerful research hypothesis. As you’re reading and preparing your hypothesis, you’ll also read other hypotheses. These can help guide you on what works, and what doesn’t, when it comes to writing a strong research hypothesis.

Here are a few generic examples to get you started.

Eating an apple each day, after the age of 60, will result in a reduction of frequency of physician visits.

Budget airlines are more likely to receive more customer complaints. A budget airline is defined as an airline that offers lower fares and fewer amenities than a traditional full-service airline. (Note that the term “budget airline” is included in the hypothesis.

Workplaces that offer flexible working hours report higher levels of employee job satisfaction than workplaces with fixed hours.

Each of the above examples are specific, observable and measurable, and the statement of prediction can be verified or shown to be false by utilizing standard experimental practices. It should be noted, however, that often your hypothesis will change as your research progresses.

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Elsevier’s Language Editing Plus service can help ensure that your research hypothesis is well-designed, and articulates your research and conclusions. Our most comprehensive editing package, you can count on a thorough language review by native-English speakers who are PhDs or PhD candidates. We’ll check for effective logic and flow of your manuscript, as well as document formatting for your chosen journal, reference checks, and much more.

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• Researching
• 7. Hypothesis

How to write a hypothesis

Once you have created your three topic sentences , you are ready to create your hypothesis.

What is a 'hypothesis'?

A hypothesis is a single sentence answer to the Key Inquiry Question  that clearly states what your entire essay is going to argue.

It contains both the argument and the main reasons in support of your argument. Each hypothesis should clearly state the ‘answer’ to the question, followed by a ‘why’.

For Example:  

The Indigenous people of Australia were treated as second-class citizens until the 1960’s (answer) by the denial of basic political rights by State and Federal governments (why) .

How do you create a hypothesis?

Back in Step 3 of the research process, you split your Key Inquiry Question into three sub-questions .

Then at Step 6 you used the quotes from your Source Research to create answers to each of the sub-questions. These answers became your three Topic Sentences .

To create your hypothesis, you need to combine the three Topic Sentences into a single sentence answer.

By combining your three answers to the sub-questions , you are ultimately providing a complete answer to the original Key Inquiry Question .

For example:

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How To Write A Hypothesis

How To Write a Hypothesis in a Research Paper | Steps & Examples

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Published on: Aug 5, 2021

Last updated on: Mar 5, 2024

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Imagine spending hours conducting experiments, only to realize that your hypothesis is unclear or poorly constructed.

This can lead to wasted time, resources, and a lack of meaningful results.

Fortunately, by mastering the art of hypothesis writing, you can ensure that your research paper is focused and structured. 

This comprehensive guide will provide you with step-by-step instructions and examples to write a hypothesis effectively.

By the end of this guide, you will have all the knowledge to write hypotheses that drive impactful scientific research.

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What is a Hypothesis?

A hypothesis is a tentative explanation or prediction that can be tested through scientific investigation. 

It is like a roadmap that guides researchers in their quest for answers. By formulating a hypothesis, researchers make educated guesses about the relationship between variables or phenomena.

Think of a hypothesis as a detective's hunch. Just like a detective forms a theory about a crime based on evidence, a researcher develops a hypothesis based on existing knowledge and observations. 

Now that we have a basic understanding of what a hypothesis is, let's delve into the process of writing one effectively.

Variables in Hypothesis

In hypotheses, variables play a crucial role as they represent the factors that are being studied and tested. 

Let's explore two types of variables commonly found in hypotheses:

1. Independent Variable: This variable is manipulated or controlled by the researcher. It is the factor believed to have an effect on the dependent variable. Here's an example:

Hypothesis: "Increasing study time (independent variable) leads to improved test scores (dependent variable) in students."

In this hypothesis, the independent variable is the study time, which the researcher can manipulate to observe its impact on the test scores.

2. Dependent Variable: This variable is the outcome or response that is measured or observed as a result of the changes in the independent variable. Here's an example:

Hypothesis: "Exposure to sunlight (independent variable) affects plant growth (dependent variable)."

In this hypothesis, the dependent variable is plant growth, which is expected to be influenced by the independent variable, sunlight exposure. The researcher measures or observes the changes in plant growth based on the different levels of sunlight exposure.

Research Question vs Hypothesis

A research question is an inquiry that defines the focus and direction of a research study. A hypothesis, on the other hand, is a tentative statement that suggests a relationship between variables or predicts the outcome of a research study.

Hypothesis vs. Prediction

The difference between a hypothesis and a prediction is slight, but it's critical to understand. 

Hypotheses are a great way to explain why something happens based on scientific methods. A prediction is a statement that says something will happen based on what has been observed.

A hypothesis is a statement with variables. A prediction is a statement that says what will happen in the future.

Theory vs. Hypothesis

The theory and hypothesis have some differences between them.

• A hypothesis is the explanation of a phenomenon that will be supported through scientific methods. 
• A theory is a well-substantiated and already-tested explanation backed by evidence.  

To turn a hypothesis into a theory, you need to test it in different situations and with strong evidence. Theories can also be used to make predictions about something that is not understood. Once you have predictions, you can turn them into hypotheses that can be tested.

How to Develop a Hypothesis Step by Step?

Developing a hypothesis is an important step in scientific research, as it sets the foundation for designing experiments and testing theories. 

Let's explore the step-by-step process of developing a hypothesis, using the example of studying the effects of exercise on sleep quality.

Step 1. Ask a Question

To begin, ask a specific question that focuses on the relationship between variables. In our example, the question could be: "Does regular exercise have a positive impact on sleep quality?"

Step 2. Do Background Research

Before formulating your hypothesis, conduct preliminary research to gather existing knowledge on the topic. 

Review scientific studies, articles, and relevant literature to understand the current understanding of exercise and its potential effects on sleep quality. This research will provide a foundation for formulating your hypothesis.

Step 3. Develop Your Hypothesis

Based on your question and preliminary research, formulate a hypothesis that predicts the expected relationship between variables. In our example, the hypothesis could be: 

"Regular exercise has a positive influence on sleep quality, resulting in improved sleep duration and reduced sleep disturbances."

Step 4. Refine Your Hypothesis

Refine your hypothesis by making it more specific and testable. Specify the variables involved and the anticipated outcomes in clear terms. For instance: 

"Engaging in moderate-intensity aerobic exercise for at least 30 minutes, three times a week, will lead to an increase in total sleep time and a decrease in the frequency of sleep disruptions."

Step 5. Express Your Hypothesis in Three Forms

To ensure comprehensiveness, phrase your hypothesis in three different ways: as a simple statement, as a positive correlation, and as a negative correlation. This will cover different perspectives and potential outcomes. 

Using our example:

• Simple Statement: "Regular exercise positively affects sleep quality."
• Positive Correlation: "As the frequency of regular exercise increases, sleep quality improves."
• Negative Correlation: "A lack of regular exercise is associated with poorer sleep quality."

Step 6. Construct a Null Hypothesis

In addition to the main hypothesis, it is important to write a null hypothesis. The null hypothesis assumes that there is no significant relationship between the variables being studied. 

The example below shows how to state the null hypothesis in a research paper: 

By following these steps, you can develop a well-structured and testable hypothesis that serves as a guiding framework for your scientific research.

Types of Research Hypotheses with Examples

Hypotheses come in various forms, depending on the nature of the research and the relationship between variables. 

Here are seven common types of hypotheses along with examples:

• Simple Hypothesis: A straightforward statement about the expected relationship between variables.

Example: "Increasing fertilizer dosage will lead to higher crop yields."

• Complex Hypothesis: A hypothesis that suggests a more intricate relationship between multiple variables.

Example: "The interaction of genetic factors and environmental stressors contributes to the development of certain mental disorders."

• Directional Hypothesis: A hypothesis that predicts the specific direction of the relationship between variables.

Example: "As temperature decreases, the viscosity of the liquid will increase."

• Non-Directional Hypothesis: A hypothesis that suggests a relationship between variables without specifying the direction.

Example: "There is a correlation between caffeine consumption and anxiety levels."

• Null Hypothesis: A hypothesis that assumes no significant relationship between variables.

Example: "There is no difference in exam performance between students who study in silence and students who listen to music."

• Alternative Hypothesis: A hypothesis that contradicts or offers an alternative explanation to the null hypothesis.

Example: "There is a significant difference in weight loss between individuals following a low-carb diet and those following a low-fat diet."

• Associative Hypothesis: A hypothesis that suggests a relationship between variables without implying causality.

Example: "There is a correlation between exercise frequency and cardiovascular health."

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What Makes a Good Hypothesis? 5 Key Elements

Crafting a good hypothesis is essential for conducting effective scientific research. A well-formed hypothesis sets the stage for meaningful experiments. 

Here are some key characteristics that make a hypothesis strong:

1. Testable and Specific

A good hypothesis should be testable through observation or experimentation. It should be formulated in a way that allows researchers to gather data and evidence to support or refute it. 

When writing a research hypothesis, it is crucial to structure it in a manner that suggests clear ways to measure or observe the variables involved.

2. Grounded in Existing Knowledge

A strong hypothesis is built upon a foundation of existing knowledge and understanding of the topic. By connecting your hypothesis to previous findings, you ensure that your research contributes to the broader scientific knowledge. 

This incorporation of existing knowledge aligns with the concept of research hypotheses, where hypotheses are framed based on the understanding of the subject from previous studies.

3. Falsifiable

A good hypothesis must be falsifiable, meaning that it can be proven false if it is indeed false. This principle is important because it allows for rigorous testing and prevents researchers from making claims that are impossible to verify or disprove. 

This aligns with the idea of statistical hypothesis, where hypotheses need to be formulated in a way that allows statistical testing to determine their validity.

4. Clearly Defines Variables

A well-formulated hypothesis clearly identifies the independent and dependent variables involved in the research. It specifies the relationship between two variables and states what researchers expect to find during the study. 

The clarity in defining variables is a crucial aspect of developing logical hypotheses.

5. Supported by Logic and Reasoning

A good hypothesis is logical and based on sound reasoning. It should be supported by evidence and a plausible rationale. The relationship between two variables proposed in the hypothesis should be grounded in a solid understanding of cause-and-effect relationships and theories.

A strong hypothesis, whether it is a research hypothesis, statistical hypothesis, or logical hypothesis, encompasses these key elements. By incorporating these elements you lay the groundwork for a robust and meaningful research study.

Hypothesis Examples 

Here are a few more examples for you to look at and get a better understanding!

How to Write a Hypothesis in Research

Research Question: "Does exposure to violent video games increase aggressive behavior in adolescents?"

Hypothesis 1: "Adolescents who are exposed to violent video games will display higher levels of aggressive behavior compared to those who are not exposed."

Hypothesis 2: "There is a positive correlation between the amount of time spent playing violent video games and the level of aggressive behavior exhibited by adolescents."

How to Write a Hypothesis for a Lab Report:

Lab Experiment: Testing the effect of different fertilizers on plant growth.

Hypothesis 1: "Plants treated with fertilizer A will exhibit greater growth in terms of height and leaf count compared to plants treated with fertilizer B."

Hypothesis 2: "There is a significant difference in the growth rate of plants when exposed to different types of fertilizers."

How to Write a Hypothesis in a Report:

Report Topic: Investigating the impact of social media usage on self-esteem.

Hypothesis 1: "Individuals who spend more time on social media will report lower levels of self-esteem compared to those who spend less time on social media."

Hypothesis 2: "There is an inverse relationship between the frequency of social media use and self-esteem levels among individuals."

Example of Hypothesis in a Research Proposal:

Crafting hypotheses in a research proposal is pivotal for outlining the research aims and guiding the investigative process. Here's an example of a hypothesis within a research proposal:

Research Proposal Topic: Investigating the impact of social media usage on adolescents' self-esteem levels.

Hypothesis: "Adolescents who spend more time on social media platforms will have lower self-esteem levels compared to those who spend less time on social media."

How To Write a Hypothesis Psychology

Research Topic: Investigating the impact of mindfulness meditation on reducing symptoms of anxiety in college students.

Hypothesis 1: "College students who regularly practice mindfulness meditation will report lower levels of anxiety compared to those who do not engage in mindfulness practices."

Hypothesis 2: "There will be a significant decrease in anxiety scores among college students who undergo a structured mindfulness meditation program compared to a control group receiving no intervention."

How to Write a Hypothesis for a Research Paper:

 Research Paper Topic: Examining the effect of mindfulness meditation on stress reduction.

Hypothesis 1: "Participating in regular mindfulness meditation practice will result in a significant decrease in perceived stress levels among participants."

Hypothesis 2: "There is a positive association between the frequency of mindfulness meditation practice and the reduction of stress levels in individuals."

How to Write a Hypothesis for Qualitative Research:

Qualitative Research Topic: Exploring the experiences of first-time mothers during the postpartum period.

Hypothesis 1: "First-time mothers will report feelings of increased anxiety and stress during the early weeks of the postpartum period."

Hypothesis 2: "There will be a common theme of adjustment challenges among first-time mothers in their narratives about the postpartum experience."

Good and Bad Hypothesis Example

Below are examples of good and bad hypotheses, along with their corresponding research question and hypothesis examples:

In conclusion, a well-crafted hypothesis sets the stage for designing experiments, collecting data, and drawing meaningful conclusions. 

By following the steps of formulating a hypothesis, researchers can ensure that their investigations are grounded in solid reasoning. AI essay writing tools can be a great help in getting ideas.

However, If you need assistance with essay writing, consider leveraging the services of CollegeEssay.org. Our team of experienced writers is dedicated to delivering high-quality, customized essays that meet your requirements and deadlines. 

Don't hesitate to visit CollegeEssay.org and benefit from our professional essay writing service . Contact us today and say goodbye to your academic paper-writing worries.

Frequently Asked Questions

What are the 3 required parts of a hypothesis.

The three main parts of the hypothesis are: 

• Problem 
• Proposed solution 
• Result 

What are 5 characteristics of a good hypothesis?

The main five characteristics of a good hypothesis are: 

• Clarity 
• Relevant to problem 
• Consistency 
• Specific 
• Testability 

What should not be characteristic of a hypothesis?

Complexity should not be a good characteristic of a hypothesis. 

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How to Write a Hypothesis With Examples and Explanations

• Icon Calendar 18 May 2024
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A hypothesis refers to a statement that predicts the findings of a research study. Basically, researchers develop propositions to provide tentative answers to research questions that address different aspects of the research question. In this case, a scholar must use existing theories and knowledge to create an assumption. Besides, a researcher focuses on testing supposed claims through different methods, like experiments, observations, and statistical analysis of the data. In practice, the findings from a study can either support or refute a hypothesis. Then, when writing a suggestion, scholars should conduct adequate research on the topic, brainstorm for ideas, draft a hypothesis, revise a draft supposition, and write a final claim in simple language. Also, these steps lead to the development of accurate and precise propositions that identify relationships between independent and dependent variables. In practice, one should rely on a cause and effect theory when developing a hypothesis.

General Aspects of Writing a Hypothesis

A hypothesis suggests a sentence as a statement that gives a prediction about the findings of a research study. Basically, researchers make a hypothesis, which acts as a tentative answer to the research question. In this case, a proposition lacks scientific or scholarly proof. Then, a reasonable hypothesis must address different aspects of the research question. In turn, researchers must base a proposition on existing theories and knowledge. Besides, it has to be testable through various methods, like experiments, observations, and statistical analysis. In practice, the findings from a study can either support or refute a working hypothesis. Therefore, a hypothesis refers to a statement that tries to predict the results of a survey.

Independent and Dependent Variables

A hypothesis in some studies must contain independent and dependent variables. For example. experimental and correlational research examines relationships between two or more variables. In turn, independent variables refer to factors that researchers can control or change. Besides, a dependent variable refers to factors that scholars observe or measure. Then, a null hypothesis of experimental and correlational studies must predict relationships between dependent and independent variables. Moreover, such predictions should not be guesses but should contain evidence from research studies.

Types of a Hypothesis

There are different types of hypotheses that researchers can develop in their studies. In this case, the following are the common types of hypotheses:

• A simple hypothesis refers to predictions of relationships between independent and dependent variables.
• A complex hypothesis predicts relationships between two or more independent and dependent variables.
• An empirical hypothesis is a working prediction that exists when a researcher tests a theory by using observations and experiments. Basically, this type of hypothesis goes through some trial and error methods to obtain the necessary findings. In some instances, researchers may change some variables around other variables.  
• A null hypothesis , denoted as H 0 , exists when a researcher believes that a relationship does not exist between independent and dependent variables. Basically, this hypothesis may exist when a researcher lacks adequate information to make a scientific prediction. Besides, inferences made from the findings attempt to disapprove or discredit a null hypothesis.  
• An alternative hypothesis , denoted as H 1 , attempts to disapprove a null hypothesis. In this case, researchers attempt to discover or affirm an alternative proposition. 
• A logical hypothesis refers to a proposed explanation of a concept that contains limited evidence. In practice, investigators intend to turn a reasonable assumption into an empirical claim. Also, researchers put theories or postulate them to the test.
• A statistical hypothesis is a claim related to studies that examine a section of the population. In this case, researchers identify a sample population and study their behaviors related to the research question. 

Crafting a Hypothesis

Researchers should focus on developing reasonable hypotheses for their studies. For example, one should consider different factors that relate to existing studies or theories. In this case, some predictions should pertain to research data and provide tentative answers to research questions. Hence, the following are the essential steps that a researcher should consider when developing a hypothesis.

Step 1. Researching

The first step in developing a hypothesis is to research and gather details related to the intended topic. Basically, researching allows a scholar to gain more knowledge concerning issues and factors and how variables change. Besides, this step will enable researchers to become familiar with the expected results. As a result, it influences a relevant hypothesis’s development.

Step 2. Asking Questions

A researcher should develop research questions before developing a hypothesis. For instance, investigators should create scientific questions that relate to the study and identified variables. In this case, brainstorming enhances the ability to determine relationships between independent and dependent variables. Basically, successful scholars remain focused on one cause and effect theory to ensure that they develop accurate ideas for a hypothesis. Therefore, the second step in developing a proposition is to brainstorm questions that reveal the relationship between independent and dependent variables. 

Step 3. Use Clear Language

Scholars should use simple and clear language when developing a hypothesis for a study. For instance, one should draft concise predictions that answer developed research questions. In practice, one should write a hypothesis in a form that proposes that an action leads to a specific result. Moreover, a researcher should not state a supposition as a question but as an affirmative statement that predicts outcomes from a particular course of action. Therefore, the third step in developing a hypothesis involves selecting a simple language for drafting scientific predictions. 

Step 4. Revising a Hypothesis

A scholar should revise a draft hypothesis to ensure that it makes a testable thesis through research and experimentation. For instance, a researcher should review a prediction to ensure that it captures relationships between at least two variables. Hence, a scholar must revise a drafted hypothesis to ensure that it captures a testable relationship between independent and dependent variables.     

Examples of a Hypothesis

1. sociology.

• Research question – How does divorce affect sociological development among young children?
• H 0 – Challenges that lead to divorce hurt young children’s social development, which affects their ability to interact with other people. 
• H 1 – Most children manage to cope with domestic challenges that lead to divorce, enabling them to realize healthy sociological development.
• Research question – How did tenebrism influence baroque art during the 16 th and 17 th centuries?
• H 0 – The origin of tenebrism had a positive impact on the dynamic appearance of baroque art.
• H 1 – Baroque art emerged as a unique art that did not have any form of external influence.

3. Geography

• Research question – To what extent does geological activity affect the Earth?
• H 0 – The movement of tectonic plates beneath the Earth’s surface results in volcanic eruptions and faults that lead to mountains and lift valleys.  
• H 1 – Mountains and valleys are natural features with little connection with geological activities like the movement of tectonic plates beneath the Earth’s surface.

4. Philosophy Hypothesis

• Research question – Do animals have rights and welfare in society?
• H 0 – Wild and domestic animals are living creatures with a right to care and protection by humans.
• H 1 – Wild and domestic animals are subordinate to humans, which implies that they do not have a right to care and protection.  
• Research question – Does the consumption of genetically modified plants cause health complications in humans?
• H 0 – Genetically modified foods are safe for human consumption and do not pose any possible health risks.
• H 1 – Genetically modified foods interfere with healthy cell development, which leads to health complications.

4. Indigenous Studies

• Research question – What role does culture play among indigenous communities?
• H 0 – Cultural practices among Aboriginals promote their identity and contribute to the members’ overall well-being.
• H 1 – cultural practices among Aboriginals do not significantly contribute to the quality of their lives.
• Research question – Does fascism exist in the twenty-first century?
• H 0 – The established forms of democracy in the twenty-first century do not allow political leaders to implement all the fascism elements.
• H 1 – Some political leaders in the twenty-first century adopt radical policies that promote the existence of fascism.
• Research question – Do neutrons have mass?
• H 0 – Neutrons are small particles that have masses.
• H 1 – Neutrons are small particles whose weight remains insignificant.

7. Health Studies

• Research question – How do evidence-based treatment approaches enhance the quality of the treatments?
• H 0 – Evidence-based treatment methods allow doctors to gather adequate and accurate information about the patient, which helps tailor treatment and care approaches to meet the patient’s needs.
• H 1 – Evidence-based approaches do not enhance the quality of the treatments since they lead to inconsistency in the care and medications given to a patient.

8. Environmental Studies

• Research question – To what extent do human activities contribute to global warming?
• H 0 – Most human activities release greenhouse gases into the atmosphere, which results in the rise of average temperatures.
• H 1 – Most human activities release insignificant amounts of greenhouse gases into the atmosphere, contributing to global warming.

Summing Up on How to Write a Good Scientific Hypothesis in a Research Paper

A hypothesis gives a prediction about the findings of a research study. Basically, researchers develop hypotheses to provide a tentative answer to research questions. In turn, some of the factors that one must consider when writing a hypothesis include:

• conduct adequate research on the topic;
• brainstorm for ideas;
• draft a hypothesis;
• revise a draft proposition;
• write a final hypothesis in simple language.

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On the role of hypotheses in science

Harald brüssow.

1 Laboratory of Gene Technology, Department of Biosystems, KU Leuven, Leuven Belgium

Associated Data

Scientific research progresses by the dialectic dialogue between hypothesis building and the experimental testing of these hypotheses. Microbiologists as biologists in general can rely on an increasing set of sophisticated experimental methods for hypothesis testing such that many scientists maintain that progress in biology essentially comes with new experimental tools. While this is certainly true, the importance of hypothesis building in science should not be neglected. Some scientists rely on intuition for hypothesis building. However, there is also a large body of philosophical thinking on hypothesis building whose knowledge may be of use to young scientists. The present essay presents a primer into philosophical thoughts on hypothesis building and illustrates it with two hypotheses that played a major role in the history of science (the parallel axiom and the fifth element hypothesis). It continues with philosophical concepts on hypotheses as a calculus that fits observations (Copernicus), the need for plausibility (Descartes and Gilbert) and for explicatory power imposing a strong selection on theories (Darwin, James and Dewey). Galilei introduced and James and Poincaré later justified the reductionist principle in hypothesis building. Waddington stressed the feed‐forward aspect of fruitful hypothesis building, while Poincaré called for a dialogue between experiment and hypothesis and distinguished false, true, fruitful and dangerous hypotheses. Theoretical biology plays a much lesser role than theoretical physics because physical thinking strives for unification principle across the universe while biology is confronted with a breathtaking diversity of life forms and its historical development on a single planet. Knowledge of the philosophical foundations on hypothesis building in science might stimulate more hypothesis‐driven experimentation that simple observation‐oriented “fishing expeditions” in biological research.

Short abstract

Scientific research progresses by the dialectic dialogue between hypothesis building and the experimental testing of these hypotheses. Microbiologists can rely on an increasing set of sophisticated experimental methods for hypothesis testing but the importance of hypothesis building in science should not be neglected. This Lilliput offers a primer on philosophical concepts on hypotheses in science.

INTRODUCTION

Philosophy of science and the theory of knowledge (epistemology) are important branches of philosophy. However, philosophy has over the centuries lost its dominant role it enjoyed in antiquity and became in Medieval Ages the maid of theology (ancilla theologiae) and after the rise of natural sciences and its technological applications many practising scientists and the general public doubt whether they need philosophical concepts in their professional and private life. This is in the opinion of the writer of this article, an applied microbiologist, shortsighted for several reasons. Philosophers of the 20th century have made important contributions to the theory of knowledge, and many eminent scientists grew interested in philosophical problems. Mathematics which plays such a prominent role in physics and increasingly also in other branches of science is a hybrid: to some extent, it is the paradigm of an exact science while its abstract aspects are deeply rooted in philosophical thinking. In the present essay, the focus is on hypothesis and hypothesis building in science, essentially it is a compilation what philosophers and scientists thought about this subject in past and present. The controversy between the mathematical mind and that of the practical mind is an old one. The philosopher, physicist and mathematician Pascal ( 1623 –1662a) wrote in his Pensées : “Mathematicians who are only mathematicians have exact minds, provided all things are explained to them by means of definitions and axioms; otherwise they are inaccurate. They are only right when the principles are quite clear. And men of intuition cannot have the patience to reach to first principles of things speculative and conceptional, which they have never seen in the world and which are altogether out of the common. The intellect can be strong and narrow, and can be comprehensive and weak.” Hypothesis building is an act both of intuition and exact thinking and I hope that theoretical knowledge about hypothesis building will also profit young microbiologists.

HYPOTHESES AND AXIOMS IN MATHEMATICS

In the following, I will illustrate the importance of hypothesis building for the history of science and the development of knowledge and illustrate it with two famous concepts, the parallel axiom in mathematics and the five elements hypothesis in physics.

Euclidean geometry

The prominent role of hypotheses in the development of science becomes already clear in the first science book of the Western civilization: Euclid's The Elements written about 300 BC starts with a set of statements called Definitions, Postulates and Common Notions that lay out the foundation of geometry (Euclid,  c.323‐c.283 ). This axiomatic approach is very modern as exemplified by the fact that Euclid's book remained for long time after the Bible the most read book in the Western hemisphere and a backbone of school teaching in mathematics. Euclid's twenty‐three definitions start with sentences such as “1. A point is that which has no part; 2. A line is breadthless length; 3. The extremities of a line are points”; and continues with the definition of angles (“8. A plane angle is the inclination to one another of two lines in a plane which meet one another and do not lie in a straight line”) and that of circles, triangles and quadrilateral figures. For the history of science, the 23rd definition of parallels is particularly interesting: “Parallel straight lines are straight lines which, being in the same plane and being produced indefinitely in both directions, do not meet one another in either direction”. This is the famous parallel axiom. It is clear that the parallel axiom cannot be the result of experimental observations, but must be a concept created in the mind. Euclid ends with five Common Notions (“1. Things which are equal to the same thing are also equal to one another, to 5. The whole is greater than the part”). The establishment of a contradiction‐free system for a branch of mathematics based on a set of axioms from which theorems were deduced was revolutionary modern. Hilbert ( 1899 ) formulated a sound modern formulation for Euclidian geometry. Hilbert's axiom system contains the notions “point, line and plane” and the concepts of “betweenness, containment and congruence” leading to five axioms, namely the axioms of Incidence (“Verknüpfung”), of Order (“Anordnung”), of Congruence, of Continuity (“Stetigkeit”) and of Parallels.

Origin of axioms

Philosophers gave various explanations for the origin of the Euclidean hypotheses or axioms. Plato considered geometrical figures as related to ideas (the true things behind the world of appearances). Aristoteles considered geometric figures as abstractions of physical bodies. Descartes perceived geometric figures as inborn ideas from extended bodies ( res extensa ), while Pascal thought that the axioms of Euclidian geometry were derived from intuition. Kant reasoned that Euclidian geometry represented a priori perceptions of space. Newton considered geometry as part of general mechanics linked to theories of measurement. Hilbert argued that the axioms of mathematical geometry are neither the result of contemplation (“Anschauung”) nor of psychological source. For him, axioms were formal propositions (“formale Aussageformen”) characterized by consistency (“Widerspruchsfreiheit”, i.e. absence of contradiction) (Mittelstrass,  1980a ).

Definitions

Axioms were also differently defined by philosophers. In Topics , Aristoteles calls axioms the assumptions taken up by one partner of a dialogue to initiate a dialectic discussion. Plato states that an axiom needs to be an acceptable or credible proposition, which cannot be justified by reference to other statements. Yet, a justification is not necessary because an axiom is an evident statement. In modern definition, axioms are methodical first sentences in the foundation of a deductive science (Mittelstrass,  1980a ). In Posterior Analytics , Aristotle defines postulates as positions which are at least initially not accepted by the dialogue partners while hypotheses are accepted for the sake of reasoning. In Euclid's book, postulates are construction methods that assure the existence of the geometric objects. Today postulates and axioms are used as synonyms while the 18th‐century philosophy made differences: Lambert defined axioms as descriptive sentences and postulates as prescriptive sentences. According to Kant, mathematical postulates create (synthesize) concepts (Mittelstrass,  1980b ). Definitions then fix the use of signs; they can be semantic definitions that explain the proper meaning of a sign in common language use (in a dictionary style) or they can be syntactic definitions that regulate the use of these signs in formal operations. Nominal definitions explain the words, while real definitions explain the meaning or the nature of the defined object. Definitions are thus essential for the development of a language of science, assuring communication and mutual understanding (Mittelstrass,  1980c ). Finally, hypotheses are also frequently defined as consistent conjectures that are compatible with the available knowledge. The truth of the hypothesis is only supposed in order to explain true observations and facts. Consequences of this hypothetical assumptions should explain the observed facts. Normally, descriptive hypotheses precede explanatory hypotheses in the development of scientific thought. Sometimes only tentative concepts are introduced as working hypotheses to test whether they have an explanatory capacity for the observations (Mittelstrass,  1980d ).

The Euclidian geometry is constructed along a logical “if→then” concept. The “if‐clause” formulates at the beginning the supposition, the “then clause” formulates the consequences from these axioms which provides a system of geometric theorems or insights. The conclusions do not follow directly from the hypothesis; this would otherwise represent self‐evident immediate conclusions. The “if‐then” concept in geometry is not used as in other branches of science where the consequences deduced from the axioms are checked against reality whether they are true, in order to confirm the validity of the hypothesis. The task in mathematics is: what can be logically deduced from a given set of axioms to build a contradiction‐free system of geometry. Whether this applies to the real world is in contrast to the situation in natural sciences another question and absolutely secondary to mathematics (Syntopicon,  1992 ).

Pascal's rules for hypotheses

In his Scientific Treatises on Geometric Demonstrations , Pascal ( 1623‐1662b ) formulates “Five rules are absolutely necessary and we cannot dispense with them without an essential defect and frequently even error. Do not leave undefined any terms at all obscure or ambiguous. Use in definitions of terms only words perfectly well known or already explained. Do not fail to ask that each of the necessary principles be granted, however clear and evident it may be. Ask only that perfectly self‐evident things be granted as axioms. Prove all propositions, using for their proof only axioms that are perfectly self‐evident or propositions already demonstrated or granted. Never get caught in the ambiguity of terms by failing to substitute in thought the definitions which restrict or define them. One should accept as true only those things whose contradiction appears to be false. We may then boldly affirm the original statement, however incomprehensible it is.”

Kant's rules on hypotheses

Kant ( 1724–1804 ) wrote that the analysis described in his book The Critique of Pure Reason “has now taught us that all its efforts to extend the bounds of knowledge by means of pure speculation, are utterly fruitless. So much the wider field lies open to hypothesis; as where we cannot know with certainty, we are at liberty to make guesses and to form suppositions. Imagination may be allowed, under the strict surveillance of reason, to invent suppositions; but these must be based on something that is perfectly certain‐ and that is the possibility of the object. Such a supposition is termed a hypothesis. We cannot imagine or invent any object or any property of an object not given in experience and employ it in a hypothesis; otherwise we should be basing our chain of reasoning upon mere chimerical fancies and not upon conception of things. Thus, we have no right to assume of new powers, not existing in nature and consequently we cannot assume that there is any other kind of community among substances than that observable in experience, any kind of presence than that in space and any kind of duration than that in time. The conditions of possible experience are for reason the only conditions of the possibility of things. Otherwise, such conceptions, although not self‐contradictory, are without object and without application. Transcendental hypotheses are therefore inadmissible, and we cannot use the liberty of employing in the absence of physical, hyperphysical grounds of explanation because such hypotheses do not advance reason, but rather stop it in its progress. When the explanation of natural phenomena happens to be difficult, we have constantly at hand a transcendental ground of explanation, which lifts us above the necessity of investigating nature. The next requisite for the admissibility of a hypothesis is its sufficiency. That is it must determine a priori the consequences which are given in experience and which are supposed to follow from the hypothesis itself.” Kant stresses another aspect when dealing with hypotheses: “It is our duty to try to discover new objections, to put weapons in the hands of our opponent, and to grant him the most favorable position. We have nothing to fear from these concessions; on the contrary, we may rather hope that we shall thus make ourselves master of a possession which no one will ever venture to dispute.”

For Kant's analytical and synthetical judgements and Difference between philosophy and mathematics (Kant, Whitehead) , see Appendices  S1 and S2 , respectively.

Poincaré on hypotheses

The mathematician‐philosopher Poincaré ( 1854 –1912a) explored the foundation of mathematics and physics in his book Science and Hypothesis . In the preface to the book, he summarizes common thinking of scientists at the end of the 19th century. “To the superficial observer scientific truth is unassailable, the logic of science is infallible, and if scientific men sometimes make mistakes, it is because they have not understood the rules of the game. Mathematical truths are derived from a few self‐evident propositions, by a chain of flawless reasoning, they are imposed not only by us, but on Nature itself. This is for the minds of most people the origin of certainty in science.” Poincaré then continues “but upon more mature reflection the position held by hypothesis was seen; it was recognized that it is as necessary to the experimenter as it is to the mathematician. And then the doubt arose if all these constructions are built on solid foundations.” However, “to doubt everything or to believe everything are two equally convenient solutions: both dispense with the necessity of reflection. Instead, we should examine with the utmost care the role of hypothesis; we shall then recognize not only that it is necessary, but that in most cases it is legitimate. We shall also see that there are several kinds of hypotheses; that some are verifiable and when once confirmed by experiment become truths of great fertility; that others may be useful to us in fixing our ideas; and finally that others are hypotheses only in appearance, and reduce to definitions or to conventions in disguise.” Poincaré argues that “we must seek mathematical thought where it has remained pure‐i.e. in arithmetic, in the proofs of the most elementary theorems. The process is proof by recurrence. We first show that a theorem is true for n  = 1; we then show that if it is true for n –1 it is true for n; and we conclude that it is true for all integers. The essential characteristic of reasoning by recurrence is that it contains, condensed in a single formula, an infinite number of syllogisms.” Syllogism is logical argument that applies deductive reasoning to arrive at a conclusion. Poincaré notes “that here is a striking analogy with the usual process of induction. But an essential difference exists. Induction applied to the physical sciences is always uncertain because it is based on the belief in a general order of the universe, an order which is external to us. Mathematical induction‐ i.e. proof by recurrence – is on the contrary, necessarily imposed on us, because it is only the affirmation of a property of the mind itself. No doubt mathematical recurrent reasoning and physical inductive reasoning are based on different foundations, but they move in parallel lines and in the same direction‐namely, from the particular to the general.”

Non‐Euclidian geometry: from Gauss to Lobatschewsky

Mathematics is an abstract science that intrinsically does not request that the structures described reflect a physical reality. Paradoxically, mathematics is the language of physics since the founder of experimental physics Galilei used Euclidian geometry when exploring the laws of the free fall. In his 1623 treatise The Assayer , Galilei ( 1564 –1642a) famously formulated that the book of Nature is written in the language of mathematics, thus establishing a link between formal concepts in mathematics and the structure of the physical world. Euclid's parallel axiom played historically a prominent role for the connection between mathematical concepts and physical realities. Mathematicians had doubted that the parallel axiom was needed and tried to prove it. In Euclidian geometry, there is a connection between the parallel axiom and the sum of the angles in a triangle being two right angles. It is therefore revealing that the famous mathematician C.F. Gauss investigated in the early 19th century experimentally whether this Euclidian theorem applies in nature. He approached this problem by measuring the sum of angles in a real triangle by using geodetic angle measurements of three geographical elevations in the vicinity of Göttingen where he was teaching mathematics. He reportedly measured a sum of the angles in this triangle that differed from 180°. Gauss had at the same time also developed statistical methods to evaluate the accuracy of measurements. Apparently, the difference of his measured angles was still within the interval of Gaussian error propagation. He did not publish the reasoning and the results for this experiment because he feared the outcry of colleagues about this unorthodox, even heretical approach to mathematical reasoning (Carnap,  1891 ‐1970a). However, soon afterwards non‐Euclidian geometries were developed. In the words of Poincaré, “Lobatschewsky assumes at the outset that several parallels may be drawn through a point to a given straight line, and he retains all the other axioms of Euclid. From these hypotheses he deduces a series of theorems between which it is impossible to find any contradiction, and he constructs a geometry as impeccable in its logic as Euclidian geometry. The theorems are very different, however, from those to which we are accustomed, and at first will be found a little disconcerting. For instance, the sum of the angles of a triangle is always less than two right angles, and the difference between that sum and two right angles is proportional to the area of the triangle. Lobatschewsky's propositions have no relation to those of Euclid, but are none the less logically interconnected.” Poincaré continues “most mathematicians regard Lobatschewsky's geometry as a mere logical curiosity. Some of them have, however, gone further. If several geometries are possible, they say, is it certain that our geometry is true? Experiments no doubt teaches us that the sum of the angles of a triangle is equal to two right angles, but this is because the triangles we deal with are too small” (Poincaré,  1854 ‐1912a)—hence the importance of Gauss' geodetic triangulation experiment. Gauss was aware that his three hills experiment was too small and thought on measurements on triangles formed with stars.

Poincaré vs. Einstein

Lobatschewsky's hyperbolic geometry did not remain the only non‐Euclidian geometry. Riemann developed a geometry without the parallel axiom, while the other Euclidian axioms were maintained with the exception of that of Order (Anordnung). Poincaré notes “so there is a kind of opposition between the geometries. For instance the sum of the angles in a triangle is equal to two right angles in Euclid's geometry, less than two right angles in that of Lobatschewsky, and greater than two right angles in that of Riemann. The number of parallel lines that can be drawn through a given point to a given line is one in Euclid's geometry, none in Riemann's, and an infinite number in the geometry of Lobatschewsky. Let us add that Riemann's space is finite, although unbounded.” As further distinction, the ratio of the circumference to the diameter of a circle is equal to π in Euclid's, greater than π in Lobatschewsky's and smaller than π in Riemann's geometry. A further difference between these geometries concerns the degree of curvature (Krümmungsmass k) which is 0 for a Euclidian surface, smaller than 0 for a Lobatschewsky and greater than 0 for a Riemann surface. The difference in curvature can be roughly compared with plane, concave and convex surfaces. The inner geometric structure of a Riemann plane resembles the surface structure of a Euclidean sphere and a Lobatschewsky plane resembles that of a Euclidean pseudosphere (a negatively curved geometry of a saddle). What geometry is true? Poincaré asked “Ought we then, to conclude that the axioms of geometry are experimental truths?” and continues “If geometry were an experimental science, it would not be an exact science. The geometric axioms are therefore neither synthetic a priori intuitions as affirmed by Kant nor experimental facts. They are conventions. Our choice among all possible conventions is guided by experimental facts; but it remains free and is only limited by the necessity of avoiding contradictions. In other words, the axioms of geometry are only definitions in disguise. What then are we to think of the question: Is Euclidean geometry true? It has no meaning. One geometry cannot be more true than another, it can only be more convenient. Now, Euclidean geometry is, and will remain, the most convenient, 1 st because it is the simplest and 2 nd because it sufficiently agrees with the properties of natural bodies” (Poincaré,  1854 ‐1912a).

Poincaré's book was published in 1903 and only a few years later Einstein published his general theory of relativity ( 1916 ) where he used a non‐Euclidean, Riemann geometry and where he demonstrated a structure of space that deviated from Euclidean geometry in the vicinity of strong gravitational fields. And in 1919, astronomical observations during a solar eclipse showed that light rays from a distant star were indeed “bent” when passing next to the sun. These physical observations challenged the view of Poincaré, and we should now address some aspects of hypotheses in physics (Carnap,  1891 ‐1970b).

HYPOTHESES IN PHYSICS

The long life of the five elements hypothesis.

Physical sciences—not to speak of biological sciences — were less developed in antiquity than mathematics which is already demonstrated by the primitive ideas on the elements constituting physical bodies. Plato and Aristotle spoke of the four elements which they took over from Thales (water), Anaximenes (air) and Parmenides (fire and earth) and add a fifth element (quinta essentia, our quintessence), namely ether. Ether is imagined a heavenly element belonging to the supralunar world. In Plato's dialogue Timaios (Plato,  c.424‐c.348 BC a ), the five elements were associated with regular polyhedra in geometry and became known as Platonic bodies: tetrahedron (fire), octahedron (air), cube (earth), icosahedron (water) and dodecahedron (ether). In regular polyhedra, faces are congruent (identical in shape and size), all angles and all edges are congruent, and the same number of faces meet at each vertex. The number of elements is limited to five because in Euclidian space there are exactly five regular polyhedral. There is in Plato's writing even a kind of geometrical chemistry. Since two octahedra (air) plus one tetrahedron (fire) can be combined into one icosahedron (water), these “liquid” elements can combine while this is not the case for combinations with the cube (earth). The 12 faces of the dodecahedron were compared with the 12 zodiac signs (Mittelstrass,  1980e ). This geometry‐based hypothesis of physics had a long life. As late as 1612, Kepler in his Mysterium cosmographicum tried to fit the Platonic bodies into the planetary shells of his solar system model. The ether theory even survived into the scientific discussion of the 19th‐century physics and the idea of a mathematical structure of the universe dominated by symmetry operations even fertilized 20th‐century ideas about symmetry concepts in the physics of elementary particles.

Huygens on sound waves in air

The ether hypothesis figures prominently in the 1690 Treatise on Light from Huygens ( 1617‐1670 ). He first reports on the transmission of sound by air when writing “this may be proved by shutting up a sounding body in a glass vessel from which the air is withdrawn and care was taken to place the sounding body on cotton that it cannot communicate its tremor to the glass vessel which encloses it. After having exhausted all the air, one hears no sound from the metal though it is struck.” Huygens comes up with some foresight when suspecting “the air is of such a nature that it can be compressed and reduced to a much smaller space than that it normally occupies. Air is made up of small bodies which float about and which are agitated very rapidly. So that the spreading of sound is the effort which these little bodies make in collisions with one another, to regain freedom when they are a little more squeezed together in the circuit of these waves than elsewhere.”

Huygens on light waves in ether

“That is not the same air but another kind of matter in which light spreads; since if the air is removed from the vessel the light does not cease to traverse it as before. The extreme velocity of light cannot admit such a propagation of motion” as sound waves. To achieve the propagation of light, Huygens invokes ether “as a substance approaching to perfect hardness and possessing springiness as prompt as we choose. One may conceive light to spread successively by spherical waves. The propagation consists nowise in the transport of those particles but merely in a small agitation which they cannot help communicate to those surrounding.” The hypothesis of an ether in outer space fills libraries of physical discussions, but all experimental approaches led to contradictions with respect to postulated properties of this hypothetical material for example when optical experiments showed that light waves display transversal and not longitudinal oscillations.

The demise of ether

Mechanical models for the transmission of light or gravitation waves requiring ether were finally put to rest by the theory of relativity from Einstein (Mittelstrass,  1980f ). This theory posits that the speed of light in an empty space is constant and does not depend on movements of the source of light or that of an observer as requested by the ether hypothesis. The theory of relativity also provides an answer how the force of gravitation is transmitted from one mass to another across an essentially empty space. In the non‐Euclidian formulation of the theory of relativity (Einstein used the Riemann geometry), there is no gravitation force in the sense of mechanical or electromagnetic forces. The gravitation force is in this formulation simply replaced by a geometric structure (space curvature near high and dense masses) of a four‐dimensional space–time system (Carnap,  1891 ‐1970c; Einstein & Imfeld,  1956 ) Gravitation waves and gravitation lens effects have indeed been experimental demonstrated by astrophysicists (Dorfmüller et al.,  1998 ).

For Aristotle's on physical hypotheses , see Appendix  S3 .

PHILOSOPHICAL THOUGHTS ON HYPOTHESES

In the following, the opinions of a number of famous scientists and philosophers on hypotheses are quoted to provide a historical overview on the subject.

Copernicus' hypothesis: a calculus which fits observations

In his book Revolutions of Heavenly Spheres Copernicus ( 1473–1543 ) reasoned in the preface about hypotheses in physics. “Since the newness of the hypotheses of this work ‐which sets the earth in motion and puts an immovable sun at the center of the universe‐ has already received a great deal of publicity, I have no doubt that certain of the savants have taken great offense.” He defended his heliocentric thesis by stating “For it is the job of the astronomer to use painstaking and skilled observations in gathering together the history of the celestial movements‐ and then – since he cannot by any line of reasoning reach the true causes of these movements‐ to think up or construct whatever causes or hypotheses he pleases such that, by the assumption of these causes, those same movements can be calculated from the principles of geometry for the past and the future too. This artist is markedly outstanding in both of these respects: for it is not necessary that these hypotheses should be true, or even probable; but it is enough if they provide a calculus which fits the observations.” This preface written in 1543 sounds in its arguments very modern physics. However, historians of science have discovered that it was probably written by a theologian friend of Copernicus to defend the book against the criticism by the church.

Bacon's intermediate hypotheses

In his book Novum Organum , Francis Bacon ( 1561–1626 ) claims for hypotheses and scientific reasoning “that they augur well for the sciences, when the ascent shall proceed by a true scale and successive steps, without interruption or breach, from particulars to the lesser axioms, thence to the intermediates and lastly to the most general.” He then notes “that the lowest axioms differ but little from bare experiments, the highest and most general are notional, abstract, and of no real weight. The intermediate are true, solid, full of life, and up to them depend the business and fortune of mankind.” He warns that “we must not then add wings, but rather lead and ballast to the understanding, to prevent its jumping and flying, which has not yet been done; but whenever this takes place we may entertain greater hopes of the sciences.” With respect to methodology, Bacon claims that “we must invent a different form of induction. The induction which proceeds by simple enumeration is puerile, leads to uncertain conclusions, …deciding generally from too small a number of facts. Sciences should separate nature by proper rejections and exclusions and then conclude for the affirmative, after collecting a sufficient number of negatives.”

Gilbert and Descartes for plausible hypotheses

William Gilbert introduced in his book On the Loadstone (Gilbert,  1544‐1603 ) the argument of plausibility into physical hypothesis building. “From these arguments, therefore, we infer not with mere probability, but with certainty, the diurnal rotation of the earth; for nature ever acts with fewer than with many means; and because it is more accordant to reason that the one small body, the earth, should make a daily revolution than the whole universe should be whirled around it.”

Descartes ( 1596‐1650 ) reflected on the sources of understanding in his book Rules for Direction and distinguished what “comes about by impulse, by conjecture, or by deduction. Impulse can assign no reason for their belief and when determined by fanciful disposition, it is almost always a source of error.” When speaking about the working of conjectures he quotes thoughts of Aristotle: “water which is at a greater distance from the center of the globe than earth is likewise less dense substance, and likewise the air which is above the water, is still rarer. Hence, we hazard the guess that above the air nothing exists but a very pure ether which is much rarer than air itself. Moreover nothing that we construct in this way really deceives, if we merely judge it to be probable and never affirm it to be true; in fact it makes us better instructed. Deduction is thus left to us as the only means of putting things together so as to be sure of their truth. Yet in it, too, there may be many defects.”

Care in formulating hypotheses

Locke ( 1632‐1704 ) in his treatise Concerning Human Understanding admits that “we may make use of any probable hypotheses whatsoever. Hypotheses if they are well made are at least great helps to the memory and often direct us to new discoveries. However, we should not take up any one too hastily.” Also, practising scientists argued against careless use of hypotheses and proposed remedies. Lavoisier ( 1743‐1794 ) in the preface to his Element of Chemistry warned about beaten‐track hypotheses. “Instead of applying observation to the things we wished to know, we have chosen rather to imagine them. Advancing from one ill‐founded supposition to another, we have at last bewildered ourselves amidst a multitude of errors. These errors becoming prejudices, are adopted as principles and we thus bewilder ourselves more and more. We abuse words which we do not understand. There is but one remedy: this is to forget all that we have learned, to trace back our ideas to their sources and as Bacon says to frame the human understanding anew.”

Faraday ( 1791–1867 ) in a Speculation Touching Electric Conduction and the Nature of Matter highlighted the fundamental difference between hypotheses and facts when noting “that he has most power of penetrating the secrets of nature, and guessing by hypothesis at her mode of working, will also be most careful for his own safe progress and that of others, to distinguish that knowledge which consists of assumption, by which I mean theory and hypothesis, from that which is the knowledge of facts and laws; never raising the former to the dignity or authority of the latter.”

Explicatory power justifies hypotheses

Darwin ( 1809 –1882a) defended the conclusions and hypothesis of his book The Origin of Species “that species have been modified in a long course of descent. This has been affected chiefly through the natural selection of numerous, slight, favorable variations.” He uses a post hoc argument for this hypothesis: “It can hardly be supposed that a false theory would explain, to so satisfactory a manner as does the theory of natural selection, the several large classes of facts” described in his book.

The natural selection of hypotheses

In the concluding chapter of The Descent of Man Darwin ( 1809 –1882b) admits “that many of the views which have been advanced in this book are highly speculative and some no doubt will prove erroneous.” However, he distinguished that “false facts are highly injurious to the progress of science for they often endure long; but false views do little harm for everyone takes a salutory pleasure in proving their falseness; and when this is done, one path to error is closed and the road to truth is often at the same time opened.”

The American philosopher William James ( 1842–1907 ) concurred with Darwin's view when he wrote in his Principles of Psychology “every scientific conception is in the first instance a spontaneous variation in someone'’s brain. For one that proves useful and applicable there are a thousand that perish through their worthlessness. The scientific conceptions must prove their worth by being verified. This test, however, is the cause of their preservation, not of their production.”

The American philosopher J. Dewey ( 1859‐1952 ) in his treatise Experience and Education notes that “the experimental method of science attaches more importance not less to ideas than do other methods. There is no such thing as experiment in the scientific sense unless action is directed by some leading idea. The fact that the ideas employed are hypotheses, not final truths, is the reason why ideas are more jealously guarded and tested in science than anywhere else. As fixed truths they must be accepted and that is the end of the matter. But as hypotheses, they must be continuously tested and revised, a requirement that demands they be accurately formulated. Ideas or hypotheses are tested by the consequences which they produce when they are acted upon. The method of intelligence manifested in the experimental method demands keeping track of ideas, activities, and observed consequences. Keeping track is a matter of reflective review.”

The reductionist principle

James ( 1842‐1907 ) pushed this idea further when saying “Scientific thought goes by selection. We break the solid plenitude of fact into separate essences, conceive generally what only exists particularly, and by our classifications leave nothing in its natural neighborhood. The reality exists as a plenum. All its part are contemporaneous, but we can neither experience nor think this plenum. What we experience is a chaos of fragmentary impressions, what we think is an abstract system of hypothetical data and laws. We must decompose each chaos into single facts. We must learn to see in the chaotic antecedent a multitude of distinct antecedents, in the chaotic consequent a multitude of distinct consequents.” From these considerations James concluded “even those experiences which are used to prove a scientific truth are for the most part artificial experiences of the laboratory gained after the truth itself has been conjectured. Instead of experiences engendering the inner relations, the inner relations are what engender the experience here.“

Following curiosity

Freud ( 1856–1939 ) considered curiosity and imagination as driving forces of hypothesis building which need to be confronted as quickly as possible with observations. In Beyond the Pleasure Principle , Freud wrote “One may surely give oneself up to a line of thought and follow it up as far as it leads, simply out of scientific curiosity. These innovations were direct translations of observation into theory, subject to no greater sources of error than is inevitable in anything of the kind. At all events there is no way of working out this idea except by combining facts with pure imagination and thereby departing far from observation.” This can quickly go astray when trusting intuition. Freud recommends “that one may inexorably reject theories that are contradicted by the very first steps in the analysis of observation and be aware that those one holds have only a tentative validity.”

Feed‐forward aspects of hypotheses

The geneticist Waddington ( 1905–1975 ) in his essay The Nature of Life states that “a scientific theory cannot remain a mere structure within the world of logic, but must have implications for action and that in two rather different ways. It must involve the consequence that if you do so and so, such and such result will follow. That is to say it must give, or at least offer, the possibility of controlling the process. Secondly, its value is quite largely dependent on its power of suggesting the next step in scientific advance. Any complete piece of scientific work starts with an activity essentially the same as that of an artist. It starts by asking a relevant question. The first step may be a new awareness of some facet of the world that no one else had previously thought worth attending to. Or some new imaginative idea which depends on a sensitive receptiveness to the oddity of nature essentially similar to that of the artist. In his logical analysis and manipulative experimentation, the scientist is behaving arrogantly towards nature, trying to force her into his categories of thought or to trick her into doing what he wants. But finally he has to be humble. He has to take his intuition, his logical theory and his manipulative skill to the bar of Nature and see whether she answers yes or no; and he has to abide by the result. Science is often quite ready to tolerate some logical inadequacy in a theory‐or even a flat logical contradiction like that between the particle and wave theories of matter‐so long as it finds itself in the possession of a hypothesis which offers both the possibility of control and a guide to worthwhile avenues of exploration.”

Poincaré: the dialogue between experiment and hypothesis

Poincaré ( 1854 –1912b) also dealt with physics in Science and Hypothesis . “Experiment is the sole source of truth. It alone can teach us certainty. Cannot we be content with experiment alone? What place is left for mathematical physics? The man of science must work with method. Science is built up of facts, as a house is built of stones, but an accumulation of facts is no more a science than a heap of stones is a house. It is often said that experiments should be made without preconceived concepts. That is impossible. Without the hypothesis, no conclusion could have been drawn; nothing extraordinary would have been seen; and only one fact the more would have been catalogued, without deducing from it the remotest consequence.” Poincaré compares science to a library. Experimental physics alone can enrich the library with new books, but mathematical theoretical physics draw up the catalogue to find the books and to reveal gaps which have to be closed by the purchase of new books.

Poincaré: false, true, fruitful and dangerous hypotheses

Poincaré continues “we all know that there are good and bad experiments. The latter accumulate in vain. Whether there are hundred or thousand, one single piece of work will be sufficient to sweep them into oblivion. Bacon invented the term of an experimentum crucis for such experiments. What then is a good experiment? It is that which teaches us something more than an isolated fact. It is that which enables us to predict and to generalize. Experiments only gives us a certain number of isolated points. They must be connected by a continuous line and that is true generalization. Every generalization is a hypothesis. It should be as soon as possible submitted to verification. If it cannot stand the test, it must be abandoned without any hesitation. The physicist who has just given up one of his hypotheses should rejoice, for he found an unexpected opportunity of discovery. The hypothesis took into account all the known factors which seem capable of intervention in the phenomenon. If it is not verified, it is because there is something unexpected. Has the hypothesis thus rejected been sterile? Far from it. It has rendered more service than a true hypothesis.” Poincaré notes that “with a true hypothesis only one fact the more would have been catalogued, without deducing from it the remotest consequence. It may be said that the wrong hypothesis has rendered more service than a true hypothesis.” However, Poincaré warns that “some hypotheses are dangerous – first and foremost those which are tacit and unconscious. And since we make them without knowing them, we cannot get rid of them.” Poincaré notes that here mathematical physics is of help because by its precision one is compelled to formulate all the hypotheses, revealing also the tacit ones.

Arguments for the reductionist principle

Poincaré also warned against multiplying hypotheses indefinitely: “If we construct a theory upon multiple hypotheses, and if experiment condemns it, which of the premisses must be changed?” Poincaré also recommended to “resolve the complex phenomenon given directly by experiment into a very large number of elementary phenomena. First, with respect to time. Instead of embracing in its entirety the progressive development of a phenomenon, we simply try to connect each moment with the one immediately preceding. Next, we try to decompose the phenomenon in space. We must try to deduce the elementary phenomenon localized in a very small region of space.” Poincaré suggested that the physicist should “be guided by the instinct of simplicity, and that is why in physical science generalization so readily takes the mathematical form to state the problem in the form of an equation.” This argument goes back to Galilei ( 1564 –1642b) who wrote in The Two Sciences “when I observe a stone initially at rest falling from an elevated position and continually acquiring new increments of speed, why should I not believe that such increases take place in a manner which is exceedingly simple and rather obvious to everybody? If now we examine the matter carefully we find no addition or increment more simple than that which repeats itself always in the same manner. It seems we shall not be far wrong if we put the increment of speed as proportional to the increment of time.” With a bit of geometrical reasoning, Galilei deduced that the distance travelled by a freely falling body varies as the square of the time. However, Galilei was not naïve and continued “I grant that these conclusions proved in the abstract will be different when applied in the concrete” and considers disturbances cause by friction and air resistance that complicate the initially conceived simplicity.

Four sequential steps of discovery…

Some philosophers of science attributed a fundamental importance to observations for the acquisition of experience in science. The process starts with accidental observations (Aristotle), going to systematic observations (Bacon), leading to quantitative rules obtained with exact measurements (Newton and Kant) and culminating in observations under artificially created conditions in experiments (Galilei) (Mittelstrass,  1980g ).

…rejected by Popper and Kant

In fact, Newton wrote that he had developed his theory of gravitation from experience followed by induction. K. Popper ( 1902‐1994 ) in his book Conjectures and Refutations did not agree with this logical flow “experience leading to theory” and that for several reasons. This scheme is according to Popper intuitively false because observations are always inexact, while theory makes absolute exact assertions. It is also historically false because Copernicus and Kepler were not led to their theories by experimental observations but by geometry and number theories of Plato and Pythagoras for which they searched verifications in observational data. Kepler, for example, tried to prove the concept of circular planetary movement influenced by Greek theory of the circle being a perfect geometric figure and only when he could not demonstrate this with observational data, he tried elliptical movements. Popper noted that it was Kant who realized that even physical experiments are not prior to theories when quoting Kant's preface to the Critique of Pure Reason : “When Galilei let his globes run down an inclined plane with a gravity which he has chosen himself, then a light dawned on all natural philosophers. They learnt that our reason can only understand what it creates according to its own design; that we must compel Nature to answer our questions, rather than cling to Nature's apron strings and allow her to guide us. For purely accidental observations, made without any plan having been thought out in advance, cannot be connected by a law‐ which is what reason is searching for.” From that reasoning Popper concluded that “we ourselves must confront nature with hypotheses and demand a reply to our questions; and that lacking such hypotheses, we can only make haphazard observations which follow no plan and which can therefore never lead to a natural law. Everyday experience, too, goes far beyond all observations. Everyday experience must interpret observations for without theoretical interpretation, observations remain blind and uninformative. Everyday experience constantly operates with abstract ideas, such as that of cause and effect, and so it cannot be derived from observation.” Popper agreed with Kant who said “Our intellect does not draw its laws from nature…but imposes them on nature”. Popper modifies this statement to “Our intellect does not draw its laws from nature, but tries‐ with varying degrees of success – to impose upon nature laws which it freely invents. Theories are seen to be free creations of our mind, the result of almost poetic intuition. While theories cannot be logically derived from observations, they can, however, clash with observations. This fact makes it possible to infer from observations that a theory is false. The possibility of refuting theories by observations is the basis of all empirical tests. All empirical tests are therefore attempted refutations.”

OUTLOOK: HYPOTHESES IN BIOLOGY

Is biology special.

Waddington notes that “living organisms are much more complicated than the non‐living things. Biology has therefore developed more slowly than sciences such as physics and chemistry and has tended to rely on them for many of its basic ideas. These older physical sciences have provided biology with many firm foundations which have been of the greatest value to it, but throughout most of its history biology has found itself faced with the dilemma as to how far its reliance on physics and chemistry should be pushed” both with respect to its experimental methods and its theoretical foundations. Vitalism is indeed such a theory maintaining that organisms cannot be explained solely by physicochemical laws claiming specific biological forces active in organisms. However, efforts to prove the existence of such vital forces have failed and today most biologists consider vitalism a superseded theory.

Biology as a branch of science is as old as physics. If one takes Aristotle as a reference, he has written more on biology than on physics. Sophisticated animal experiments were already conducted in the antiquity by Galen (Brüssow, 2022 ). Alertus Magnus displayed biological research interest during the medieval time. Knowledge on plants provided the basis of medical drugs in early modern times. What explains biology's decreasing influence compared with the rapid development of physics by Galilei and Newton? One reason is the possibility to use mathematical equations to describe physical phenomena which was not possible for biological phenomena. Physics has from the beginning displayed a trend to few fundamental underlying principles. This is not the case for biology. With the discovery of new continents, biologists were fascinated by the diversity of life. Diversity was the conducting line of biological thinking. This changed only when taxonomists and comparative anatomists revealed recurring pattern in this stunning biological variety and when Darwin provided a theoretical concept to understand variation as a driving force in biology. Even when genetics and molecular biology allowed to understand biology from a few universally shared properties, such as a universal genetic code, biology differed in fundamental aspects from physics and chemistry. First, biology is so far restricted to the planet earth while the laws of physic and chemistry apply in principle to the entire universe. Second, biology is to a great extent a historical discipline; many biological processes cannot be understood from present‐day observations because they are the result of historical developments in evolution. Hence, the importance of Dobzhansky's dictum that nothing makes sense in biology except in the light of evolution. The great diversity of life forms, the complexity of processes occurring in cells and their integration in higher organisms and the importance of a historical past for the understanding of extant organisms, all that has delayed the successful application of mathematical methods in biology or the construction of theoretical frameworks in biology. Theoretical biology by far did not achieve a comparable role as theoretical physics which is on equal foot with experimental physics. Many biologists are even rather sceptical towards a theoretical biology and see progress in the development of ever more sophisticated experimental methods instead in theoretical concepts expressed by new hypotheses.

Knowledge from data without hypothesis?

Philosophers distinguish rational knowledge ( cognitio ex principiis ) from knowledge from data ( cognitio ex data ). Kant associates these two branches with natural sciences and natural history, respectively. The latter with descriptions of natural objects as prominently done with systematic classification of animals and plants or, where it is really history, when describing events in the evolution of life forms on earth. Cognitio ex data thus played a much more prominent role in biology than in physics and explains why the compilation of data and in extremis the collection of museum specimen characterizes biological research. To account for this difference, philosophers of the logical empiricism developed a two‐level concept of science languages consisting of a language of observations (Beobachtungssprache) and a language of theories (Theoriesprache) which are linked by certain rules of correspondence (Korrespondenzregeln) (Carnap,  1891 –1970d). If one looks into leading biological research journals, it becomes clear that biology has a sophisticated language of observation and a much less developed language of theories.

Do we need more philosophical thinking in biology or at least a more vigorous theoretical biology? The breathtaking speed of progress in experimental biology seems to indicate that biology can well develop without much theoretical or philosophical thinking. At the same time, one could argue that some fields in biology might need more theoretical rigour. Microbiologists might think on microbiome research—one of the breakthrough developments of microbiology research in recent years. The field teems with fascinating, but ill‐defined terms (our second genome; holobionts; gut–brain axis; dysbiosis, symbionts; probiotics; health benefits) that call for stricter definitions. One might also argue that biologists should at least consider the criticism of Goethe ( 1749–1832 ), a poet who was also an active scientist. In Faust , the devil ironically teaches biology to a young student.

“Wer will was Lebendigs erkennen und beschreiben, Sucht erst den Geist herauszutreiben, Dann hat er die Teile in seiner Hand, Fehlt, leider! nur das geistige Band.” (To docket living things past any doubt. You cancel first the living spirit out: The parts lie in the hollow of your hand, You only lack the living thing you banned).

We probably need both in biology: more data and more theory and hypotheses.

CONFLICT OF INTEREST

The author reports no conflict of interest.

FUNDING INFORMATION

No funding information provided.

Supporting information

Appendix S1

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Over the course of studying in college, you will inevitably need to pen a bunch of Argumentative Essays on Hypothesis. Lucky you if linking words together and transforming them into meaningful text comes naturally to you; if it's not the case, you can save the day by finding a previously written Hypothesis Argumentative Essay example and using it as a template to follow.

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- Abstract This paper provides a detailed account of the theoretical issues that have existed with the researches on terrorism and also provides a clear view of the critical perspectives on terrorism researches. The study identifies extensive literature on terrorism based studies and offers a critical analysis of the approaches used and segregates between the strengths and weaknesses of the approaches that exist. The results reveal that mixed methodologies with epistemological design are adequate for terrorism researches and it is beneficial to avoid a judgmental attitude however the proposed system also provides a technique for customized selection of methodology.

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Hypothesis Testing in Healthcare Decision-Making Essay

Introduction.

Hypothesis testing plays a proficient role in the deductive and inductive derivation of insights across distinctive industries. Research indicates that developing a hypothesis in the healthcare sector is a statistical inference encompassing the comparative analysis of a causal or correlation perspective (Liu et al., 2022). Primarily, hypothesis testing is an initiative optimally utilized to quantify the strength of evidence parallel to the sample data. Therefore, the practice is a conductive factor in effective decision-making in medical care due to its attribution of establishing objective overviews on pertinent matters. The testing of a thesis is a strategic initiative that profoundly contributes to sustainable management and advancement in the healthcare mainframe.

Over the decades, the dynamism of sociocultural and economic practices fostered the emergence of various medical problems. One of the critical outliers to solving the challenges in the healthcare sector enshrines objectively demonstrating the interplay between the independent and dependent variables. Transcendentally, researchers agree that the use of hypothesis renders the identification of vital elements in the spectral issue while ascertaining the core approach to determine effective and functional decision-making among the practitioners (Prieto et al., 2021). An excellent example is a comparative analysis between obesity and lifestyle habits. The development of a hypothesis that addresses the pivotal effect between lifestyle habits and obesity further maps the trickle-down effect on individuals’ well-being.

In conclusion, it is the responsibility of professionals to exploit hypothesis testing strategies due to the objective effects. One of the primary virtues in the healthcare sector enshrines promoting the welfare of the patients. Therefore, it is critical to establish factorial baselines affirming correlations and causal perspectives. As a result, the stakeholders access ultimately actionable intelligence for sustainable decision-making. Hypothesis testing is an initiative that significantly influences the quality of medical care as a multidimensional phenomenon.

Liu, X., Zhang, Z., & Wang, L. (2022). Bayesian hypothesis testing of mediation: Methods and the impact of prior odds specifications . Behavior Research Methods , 1-13. Web.

Prieto, C., Kavetski, D., Le Vine, N., Álvarez, C., & Medina, R. (2021). Identification of dominant hydrological mechanisms using Bayesian inference, multiple statistical hypothesis testing, and flexible models . Water Resources Research , 57 (8), e2020WR028338. Web.

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