Writing Hypotheses


What is a hypothesis and why do I need one?

Developing a hypothesis is the next step in the scientific method after you’ve developed your research question. (For more information on developing a research question, check out our last blog post. A hypothesis is essentially a tentative explanation related to your research question. Sometimes referred to as an ‘educated guess’, a hypothesis is a tentative, testable, and falsifiable statement that explains some observed phenomenon in nature based on previous research, observations and experiences. Hypotheses are a crucial step in the scientific method because they narrow down what you are going to measure while guiding your research. Alexander Toledo, a PhD in Biomedical Sciences and expert in developing scientific experiments that use the scientific method, claims a hypothesis is crucial for a sound and well-developed experiment and emphasizes how the hypothesis should contribute to the solution or answer to the research question (2011).

*Just a note*
Hypotheses are never ‘right’ or wrong’ but are ‘supported’ or ‘unsupported’ by the data and evidence you collect. The goal of your experiment should never be to prove your hypothesis right (or another one wrong). Rather, the goal of a scientific experiment is to learn more about how the natural world works. Make sure your hypothesis is capable of being supported or unsupported (Cohen 2013). Remember, it’s okay if your data doesn’t support your hypothesis! Also, make sure your hypothesis isn’t ‘loaded’. A loaded hypothesis is one that sets out to prove someone or something wrong by incorporating individual biases. We want hypotheses to remain neutral in an effort to keep science as objective as possible.

How do I write one?

A good hypothesis should guide your research and narrow down what your variables are. Hypotheses should contain an independent variable and a dependent variable. An independent variable is what the scientist (you!) changes or manipulates during the experiment. A dependent variable is what you are observing in the experiment. A simple format to follow when writing a basic scientific hypothesis containing one independent and one dependent variable is the ever popular “if, then, because” format. This format sets up the hypothesis in one concise sentence that goes something like this:

If (the independent variable) is (increased/decreased/stayed the same) then (the dependent variable) will (increase/decrease/stay the same) because (why you think this change will happen based on prior research and experiences).

Below are a few examples of good (and bad) hypotheses to get you started:

  1. If I give my roses more water then they will grow faster because water promotes rose growth.
    • This is an example of a good hypothesis (even though it may not be supported by data) because it identifies an independent variable (amount of water given to roses) and a dependent variable (rose growth) while answering a research question that asked about factors that stimulate rose growth.
  2. If I change the amount of water I give my roses then they may grow at different rates.
    • This hypothesis does not address a specific question or give a tentative explanation as to why something may happen. Make sure your hypothesis is specific! How could you make this hypothesis better?

How do I know I have a strong hypothesis?

Below is a list of criteria that can help you evaluate the strength your hypothesis:

  1. Is it related to my research question?
    • Is my hypothesis an explanation related to my research question or is it completely different?
    • Do I need multiple hypotheses to successfully address my research question?
  2. Is it falsifiable?
    • Does my hypothesis define measurable variables?
    • Is there a method to analyze my data?
    • Do I have access to the resources I need to collect my data?
    • Do I need special permissions, tools or other considerations to collect data?
  3. Is it neutral?
    • Am I doing my best to avoid my individual biases when answering my research question?
    • Is the purpose of my experiment to prove someone else wrong?
  4. Is it simple?
    • Will my data collectors need any prior knowledge or training to collect data?
    • Do I know how to analyze the data?
  5. Is it specific?
    • Is my hypothesis unique to a particular area?
    • Did I define my variables clearly?

Important Takeaways

  • Hypotheses should directly address or be related to your research question
  • Avoid ‘loaded’ or biased hypotheses in an attempt to keep science objective
  • A good hypothesis defines independent and dependent variables
  • A hypothesis is never ‘right’ or ‘wrong’, it is ‘supported’ or ‘not supported’ by the data and evidence you collect
  • It’s okay if your hypothesis is not supported by your data!


If you have any suggestions for future topics that you would like to be covered or feedback for us please don’t hesitate to contact us at webmaster@citsci.org. Thanks!


Cohen, M. F. (2013). An introduction to logic and scientific method. Read Books Ltd.

Toledo, A. H., Flikkema, R., and L. H. Toledo-Pereyra (2011). Developing the Research Hypothesis. Journal of Investigative Surgery, 24:5, 191-194, DOI: 10.3109/08941939.2011.609449  https://doi.org/10.3109/08941939.2011.609449

The Writing Center (2017) How to Write a Research Question,  George Mason University, https://writingcenter.gmu.edu/guides/how-to-write-a-research-question

Teaching the Hypothesis. Paul K. Strode, November 2, 2014

Cover Photo: Sarah Newman

2 comments on “Writing Hypotheses”

  1. Hypotheses are not written as “if-then” statements in the real world. Look at the hypotheses in this article: they are not hypotheses but, rather, they are predictions. They do not state the “why” of the cause and the effect, which is the purpose of the hypothesis. Please find me one peer-reviewed work of research that states their hypothesis as an “if-then” statement. I’ll wait.


  2. Hi Cecilia,

    Thanks for taking the time to read and comment on our Writing Hypotheses blog post. We agree that this piece needs a rewrite to, among other things, clarify the difference between hypotheses and predictions and recognize that the particular if-then statements listed here fall in the latter category. We are actively working on a re-write of this post – if you have peer-reviewed articles you recommend for teaching hypothesis writing to your students please share them with us! We have found Strode, P.K. Hypothesis Generation in Biology: A Science Teaching Challenge & Potential Solution, to be one useful source.



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