How to write a hypothesis

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

Example hypothesis

Daily apple consumption leads to fewer doctor’s visits.

What is a hypothesis?

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.

Daily apple consumption leads to fewer doctor’s visits.

In this example, the independent variable is apple consumption — the assumed cause. The dependent variable is the frequency of doctor’s visits — the assumed effect.

Developing a hypothesis

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.

Do students who attend more lectures get better exam results?

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.

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.

Attending more lectures leads to better exam results.

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

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.

If a first-year student starts attending more lectures, then their exam scores will improve.

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

The number of lectures attended by first-year students has a positive effect on their exam scores.

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

First-year students who attended most lectures will have better exam scores than those who attended few lectures.

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 H0, while the alternative hypothesis is H1 or Ha.

H0: The number of lectures attended by first-year students has no effect on their final exam scores.
H1: The number of lectures attended by first-year students has a positive effect on their final exam scores.

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Hypothesis examples

Research question Hypothesis Null hypothesis
What are the health benefits of eating an apple a day? Increasing apple consumption in over-60s will result in decreasing frequency of doctor’s visits. Increasing apple consumption in over-60s will have no effect on frequency of doctor’s visits.
Which airlines have the most delays? Low-cost airlines are more likely to have delays than premium airlines. Low-cost and premium airlines are equally likely to have delays.
Can flexible work arrangements improve job satisfaction? Employees who have flexible working hours will report greater job satisfaction than employees who work fixed hours. There is no relationship between working hour flexibility and job satisfaction.
How effective is high school sex education at reducing teen pregnancies? Teenagers who received sex education lessons throughout high school will have lower rates of unplanned pregnancy than teenagers who did not receive any sex education. High school sex education has no effect on teen pregnancy rates.
What effect does daily use of social media have on the attention span of under-16s? There is a negative correlation between time spent on social media and attention span in under-16s. There is no relationship between social media use and attention span in under-16s.
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Shona McCombes

Shona has a bachelor's and two master's degrees, so she's an expert at writing a great thesis. She has also worked as an editor and teacher, working with students at all different levels to improve their academic writing.

15 comments

louise ferguson
October 19, 2020 at 5:55 PM

what is a good hypothesis for covid19 and effects on society?

kind regards
louise

Reply

hagos
October 7, 2020 at 9:15 PM

how can I formulate hypothesis for a research title: level of utilization family planing service among adolescent

Reply

ivd
October 21, 2020 at 12:13 PM

research questions you have to make which directly relates to the title of the topic with the help of literature review. The you can define hypothesis which will answer your research question.

Reply

tessa
October 5, 2020 at 11:50 PM

This website is the awesome it was really helpful

Reply

Kelle Glenn
September 10, 2020 at 6:23 PM

"If developing countries had the same level of refrigeration for the transportation & storage of food as developed countries, them one-third of food loss would be avoided."
I need to develop a testable hypothesis using the problem and an insulating material that I have at home - form drinking cups, pool noodles, paper, cardboard box. When I write the hypothesis I must clearly define the independent variable(how to change the insulators thickness, type, etc.) & what information I want to collect my (dependent variable) such as temperature. I should use the If... and Then... format.
Please help! The more I research the more lost I become.

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Ben
October 23, 2020 at 9:45 AM

your hypothesis may be subject to strong dependent variable such as electricity which is epileptic in most developing country and as such may hinder refrigeration.

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Noel Zhou
September 1, 2020 at 5:18 PM

This is a very simple and extremely clear explanation. Could not ask for more - Thank you Shona

Reply

Kaba sangary
August 30, 2020 at 4:42 AM

How can I write a strong hypothesis
Who are at high risk of covid 19

Reply

Bhavs
August 23, 2020 at 8:43 AM

very educative!

Does my hypothesis work for my guiding question?

Guiding Question: Does the amount of sugar added onto the ice cubes affect the amount of water that has melted over a period of 20 minutes?

Hypothesis:
If I increase the number of tablespoons for sugar onto my ice cubes, then the teaspoons of water melted from the ice cubes will increase.

Reply

fatemeh
July 27, 2020 at 12:48 AM

very good and easy to follow questions, but i hoped for more qualitative example.

Reply

Shona McCombes
Shona McCombes (Scribbr-team)
July 29, 2020 at 7:41 PM

Hi Fatemeh,

Qualitative research isn't used to test hypotheses – it's more common to work with open research questions in this type of research.

However, qualitative research can be used to generate hypotheses that can later be tested through quantitative research. For example, our hypothesis about the relationship between apple consumption and doctor's visits could have been developed through an initial qualitative study that interviewed doctors and patients about dietary habits and health outcomes. The qualitative data helps us come up with our hypothesis about a possible relationship, while a quantitative study can be used to test it.

Hope that helps!

Reply

Sana
August 24, 2020 at 3:13 AM

Hi Shona,

Thanks for your explanations, my study is exactly the other way round. I have statistical study then interview study.

My question is that: should I test my hypothesis in discussion chapter?
Also, while testing the hypothesis I need to address the quantitative findings, how about qualitative ones?? How can I corporate???
Thanks,

Reply

Shona McCombes
Shona McCombes (Scribbr-team)
September 16, 2020 at 1:09 PM

Hi Sana,

The results of your hypothesis test should usually be reported in the results chapter. You can also summarize your overall findings from the qualitative data here.

In the discussion chapter, you interpret the results and explain their relevance. Here it would be appropriate to discuss similarities and differences between the qualitative and quantitative results, explaining how the two methods complement each other to give a more detailed answer to your research question.

Reply

Anis
May 8, 2020 at 9:34 PM

Very high standard yet easily understandable explanation. Superb. Many thanks.

Reply

Peter Kiptoo
December 2, 2019 at 2:37 AM

The examples you've used has made it easier for my clear understanding of the concept....now I'm ready to do my exams and pass
....Thanks Shona

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