How to Write Hypothesis

How to Write Hypothesis – One of our 10 essential words for university success, a hypothesis is one of the earliest stages of the scientific method. It’s essentially an educated guess—based on observations—of what the results of your experiment or research will be. 

If you’ve noticed that watering your plants every day makes them grow faster, your hypothesis might be “plants grow better with regular watering.” From there, you can begin experiments to test your hypothesis; in this example, you might set aside two plants, water one but not the other, and then record the results to see the differences. 

The language of hypotheses always discusses variables, or the elements that you’re testing. Variables can be objects, events, concepts, etc.—whatever is observable. 

There are two types of variables: independent and dependent. Independent variables are the ones that you change for your experiment, whereas dependent variables are the ones that you can only observe. In the above example, our independent variable is how often we water the plants and the dependent variable is how well they grow. 

Hypotheses determine the direction and organization of your subsequent research methods, and that makes them a big part of writing a research paper. Ultimately the reader wants to know whether your hypothesis was proven true or false, so it must be written clearly in the introduction and/or abstract of your paper. 

Table of Contents

7 main types of hypotheses (with examples)

Depending on the nature of your research and what you expect to find, your hypothesis will fall into one or more of the seven main categories. Keep in mind that these categories are not exclusive, so the same hypothesis might qualify as several different types. 

1 Simple hypothesis

A simple hypothesis suggests only the relationship between two variables: one independent and one dependent. 


  • If you stay up late, then you feel tired the next day. 
  • Turning off your phone makes it charge faster. 

2 Complex hypothesis

A complex hypothesis suggests the relationship between more than two variables, for example, two independents and one dependent, or vice versa. 


  • People who both (1) eat a lot of fatty foods and (2) have a family history of health problems are more likely to develop heart diseases. 
  • Older people who live in rural areas are happier than younger people who live in rural areas. 

3 Null hypothesis

A null hypothesis, abbreviated as H0, suggests that there is no relationship between variables. 


  • There is no difference in plant growth when using either bottled water or tap water. 
  • Professional psychics do not win the lottery more than other people. 

4 Alternative hypothesis

An alternative hypothesis, abbreviated as H1 or HA, is used in conjunction with a null hypothesis. It states the opposite of the null hypothesis, so that one and only one must be true. 


  • Plants grow better with bottled water than tap water. 
  • Professional psychics win the lottery more than other people. 

5 Logical hypothesis

A logical hypothesis suggests a relationship between variables without actual evidence. Claims are instead based on reasoning or deduction, but lack actual data.  


  • An alien raised on Venus would have trouble breathing in Earth’s atmosphere. 
  • Dinosaurs with sharp, pointed teeth were probably carnivores. 

6 Empirical hypothesis

An empirical hypothesis, also known as a “working hypothesis,” is one that is currently being tested. Unlike logical hypotheses, empirical hypotheses rely on concrete data. 


  • Customers at restaurants will tip the same even if the wait staff’s base salary is raised. 
  • Washing your hands every hour can reduce the frequency of illness. 

7 Statistical hypothesis

A statistical hypothesis is when you test only a sample of a population and then apply statistical evidence to the results to draw a conclusion about the entire population. Instead of testing everything, you test only a portion and generalize the rest based on preexisting data. 


  • In humans, the birth-gender ratio of males to females is 1.05 to 1.00.  
  • Approximately 2% of the world population has natural red hair. 

What makes a good hypothesis?

No matter what you’re testing, a good hypothesis is written according to the same guidelines. In particular, keep these five characteristics in mind: 

Cause and effect

Hypotheses always include a cause-and-effect relationship where one variable causes another to change (or not change if you’re using a null hypothesis). This can best be reflected as an if-then statement: If one variable occurs, then another variable changes. 

Testable prediction

Most hypotheses are designed to be tested (with the exception of logical hypotheses). Before committing to a hypothesis, make sure you’re actually able to conduct experiments on it. Choose a testable hypothesis with an independent variable that you have absolute control over. 

Independent and dependent variables

Define your variables in your hypothesis so your readers understand the big picture. You don’t have to specifically say which ones are independent and dependent variables, but you definitely want to mention them all. 

Candid language

Academic writing can easily get convoluted, so make sure your hypothesis remains as simple and clear as possible. Readers use your hypothesis as a contextual pillar to unify your entire paper, so there should be no confusion or ambiguity. If you’re unsure about your phrasing, try reading your hypothesis to a friend to see if they understand. 

Adherence to ethics

It’s not always about what you can test, but what you should test. Avoid hypotheses that require questionable or taboo experiments to keep ethics (and therefore, credibility) intact.

How to Write Hypothesis

1. Ask a Question

In the scientific method, the first step is to ask a question. Frame this question using the classic six: who, what, where, when, why, or how. Sample questions might include:

  • How long does it take carrots to grow?
  • Why does the sky get darker earlier in winter?
  • What happened to the dinosaurs?
  • How did we evolve from monkeys?
  • Why are students antsier on Friday afternoon?
  • How does sleep affect motivation?
  • Why do IEP accommodations work in schools?

You want the question to be specific and focused. It also needs to be researchable, of course. Once you know you can research your question from several angles, it’s time to start some preliminary research.

2. Gather Preliminary Research

It’s time to collect data. This will come in the form of case studies and academic journals, as well as your own experiments and observations.

Remember, it’s important to explore your question from all sides. Don’t let conflicting research deter you. You might come upon many naysayers as you gather background information. That doesn’t invalidate your hypothesis. In fact, you can use their findings as potential rebuttals and frame your study in such a way as to address these concerns.

For example, if you are looking at the question: “How does sleep affect motivation?”, you might find studies with conflicting research about eight hours vs. six hours of sleep. You can use these conflicting points to help to guide the creation of your hypothesis. Advertisement

3. Formulate an Answer To Your Question

After completing all your research, think about how you will answer your question and defend your position. For example, say the question you posed was:

How does sleep affect motivation?

As you start to collect basic observations and information, you’ll find that a lack of sleep creates a negative impact on learning. It decreases thought processes and makes it harder to learn anything new. Therefore, when you are tired, it’s harder to learn and requires more effort. Since it is harder, you can be less motivated to do it. Additionally, you discover that there is a point where sleep affects functioning. You use this research to answer your question.

Getting less than eight hours of sleep makes it harder to learn anything new and make new memories. This makes learning harder so you are less likely to be motivated.

4. Write a Hypothesis

With the answer to your question at the ready, it’s time to formulate your hypothesis. To write a good hypothesis, it should include:

  • Relevant variables
  • Predicted outcome
  • Who/what is being studied

Remember that your hypothesis needs to be a statement, not a question. It’s an idea, proposal or prediction. For example, a research hypothesis is formatted in an if/then statement:

If a person gets less than eight hours of sleep, then they will be less motivated at work or school.

This statement shows you:

  • who is being studied – a person
  • the variables – sleep and motivation
  • your prediction – less sleep means less motivation


5. Refine Your Hypothesis

While you might be able to stop at writing your research hypothesis, some hypotheses might be a correlation study or studying the difference between two groups. In these instances, you want to state the relationship or difference you expect to find.

A correlation hypothesis might be:

Getting less than eight hours of sleep has a negative impact on work or school motivation.

A hypothesis showing difference might be:

Those with seven or fewer hours of sleep are less motivated than those with eight or more to complete tasks.

6. Create a Null Hypothesis

Depending on your study, you may need to perform some statistical analysis on the data you collect. When forming your hypothesis statement using the scientific method, it’s important to know the difference between a null hypothesis vs. the alternative hypothesis, and how to create a null hypothesis.

  • A null hypothesis, often denoted as H0, posits that there is no apparent difference or that there is no evidence to support a difference. Using the motivation example above, the null hypothesis would be that sleep hours have no effect on motivation.
  • An alternative hypothesis, often denoted as H1, states that there is a statistically significant difference, or there is evidence to support such a difference. Going back to the same carrot example, the alternative hypothesis is that a person getting six hours of sleep has less motivation than someone getting eight hours of sleep.


A hypothesis involves a statement about what you will do, but also what you expect to happen or speculation about what could occur. Once you’ve written your hypothesis, you’ll need to test it, analyze the data and form your conclusion.

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