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A Strong Hypothesis


"If _____[I do this] _____, then _____[this]_____ will happen."

Sound familiar? It should. This formulaic approach to making a statement about what you "think" will happen is the basis of most science fair projects and much scientific exploration.

Step by Step
You can see from the basic outline of the Scientific Method below that writing your hypothesis comes early in the process:
  1. Ask a Question
  2. Do Background Research
  3. Construct a Hypothesis
  4. Test Your Hypothesis by Doing an Experiment
  5. Analyze Your Data and Draw a Conclusion
  6. Communicate Your Results

Following the scientific method, we come up with a question that we want to answer, we do some initial research, and then before we set out to answer the question by performing an experiment and observing what happens, we first clearly identify what we "think" will happen.

We make an "educated guess."

We write a hypothesis.

We set out to prove or disprove the hypothesis.

What you "think" will happen, of course, should be based on your preliminary research and your understanding of the science and scientific principles involved in your proposed experiment or study. In other words, you don't simply "guess." You're not taking a shot in the dark. You're not pulling your statement out of thin air. Instead, you make an "educated guess" based on what you already know and what you have already learned from your research.

If you keep in mind the format of a well-constructed hypothesis, you should find that writing your hypothesis is not difficult to do. You'll also find that in order to write a solid hypothesis, you need to understand what your variables are for your project. It's all connected!

If I never water my plant, it will dry out and die.

That seems like an obvious statement, right? The above hypothesis is too simplistic for most middle- to upper-grade science projects, however. As you work on deciding what question you will explore, you should be looking for something for which the answer is not already obvious or already known (to you). When you write your hypothesis, it should be based on your "educated guess" not on known data. Similarly, the hypothesis should be written before you begin your experimental procedures—not after the fact.

Hypotheses Tips

Our staff scientists offer the following tips for thinking about and writing good hypotheses.

  • The question comes first. Before you make a hypothesis, you have to clearly identify the question you are interested in studying.
  • A hypothesis is a statement, not a question. Your hypothesis is not the scientific question in your project. The hypothesis is an educated, testable prediction about what will happen.
  • Make it clear. A good hypothesis is written in clear and simple language. Reading your hypothesis should tell a teacher or judge exactly what you thought was going to happen when you started your project.
  • Keep the variables in mind. A good hypothesis defines the variables in easy-to-measure terms, like who the participants are, what changes during the testing, and what the effect of the changes will be. (For more information about identifying variables, see: Variables in Your Science Fair Project.)
  • Make sure your hypothesis is "testable." To prove or disprove your hypothesis, you need to be able to do an experiment and take measurements or make observations to see how two things (your variables) are related. You should also be able to repeat your experiment over and over again, if necessary.

    To create a "testable" hypothesis make sure you have done all of these things:

    • Thought about what experiments you will need to carry out to do the test.
    • Identified the variables in the project.
    • Included the independent and dependent variables in the hypothesis statement. (This helps ensure that your statement is specific enough.
  • Do your research. You may find many studies similar to yours have already been conducted. What you learn from available research and data can help you shape your project and hypothesis.
  • Don't bite off more than you can chew! Answering some scientific questions can involve more than one experiment, each with its own hypothesis. Make sure your hypothesis is a specific statement relating to a single experiment.

Putting it in Action

To help demonstrate the above principles and techniques for developing and writing solid, specific, and testable hypotheses, Sandra and Kristin, two of our staff scientists, offer the following good and bad examples.

Good Hypothesis Poor Hypothesis
When there is less oxygen in the water, rainbow trout suffer more lice.

Kristin says: "This hypothesis is good because it is testable, simple, written as a statement, and establishes the participants (trout), variables (oxygen in water, and numbers of lice), and predicts effect (as oxygen levels go down, the numbers of lice go up)."

Our universe is surrounded by another, larger universe, with which we can have absolutely no contact.

Kristin says: "This statement may or may not be true, but it is not a scientific hypothesis. By its very nature, it is not testable. There are no observations that a scientist can make to tell whether or not the hypothesis is correct. This statement is speculation, not a hypothesis."

Aphid-infected plants that are exposed to ladybugs will have fewer aphids after a week than aphid-infected plants which are left untreated.

Sandra says: "This hypothesis gives a clear indication of what is to be tested (the ability of ladybugs to curb an aphid infestation), is a manageable size for a single experiment, mentions the independent variable (ladybugs) and the dependent variable (number of aphids), and predicts the effect (exposure to ladybugs reduces the number of aphids)."

Ladybugs are a good natural pesticide for treating aphid infected plants.

Sandra says: "This statement is not 'bite size.' Whether or not something is a 'good natural pesticide' is too vague for a science fair project. There is no clear indication of what will be measured to evaluate the prediction."

Hypotheses in History

Throughout history, scientists have posed hypotheses and then set out to prove or disprove them. Staff Scientist Dave reminds that scientific experiments become a dialogue between and among scientists and that hypotheses are rarely (if ever) "eternal." In other words, even a hypothesis that is proven true may be displaced by the next set of research on a similar topic, whether that research appears a month or a hundred years later.

A look at the work of Sir Isaac Newton and Albert Einstein, more than 100 years apart, shows good hypothesis-writing in action.

As Dave explains, "A hypothesis is a possible explanation for something that is observed in nature. For example, it is a common observation that objects that are thrown into the air fall toward the earth. Sir Isaac Newton (1643-1727) put forth a hypothesis to explain this observation, which might be stated as 'objects with mass attract each other through a gravitational field.'"

Newton's hypothesis demonstrates the techniques for writing a good hypothesis: It is testable. It is simple. It is universal. It allows for predictions that will occur in new circumstances. It builds upon previously accumulated knowledge (e.g., Newton's work explained the observed orbits of the planets).

"As it turns out, despite its incredible explanatory power, Newton's hypothesis was wrong," says Dave. "Albert Einstein (1879-1955) provided a hypothesis that is closer to the truth, which can be stated as 'objects with mass cause space to bend.' This hypothesis discards the idea of a gravitational field and introduces the concept of space as bendable. Like Newton's hypothesis, the one offered by Einstein has all of the characteristics of a good hypothesis."

"Like all scientific ideas and explanations," says Dave, "hypotheses are all partial and temporary, lasting just until a better one comes along."

That's good news for scientists of all ages. There are always questions to answer and educated guesses to make!

If your science fair is over, leave a comment here to let us know what your hypothesis was for your project.


what if i have a paper airplane,and the factor that changes is the type of paper, how can i make a hypothesis out of it?

Hi Sala - There are a number of directions you could take with a project of this sort. For example, you could make an educated guess about which kind of paper in a paper airplane will yield a plain that will fly higher or faster or for a longer duration? You would just pick one. Figure out what you want to measure, and then write a hypothesis about what you think will happen.

~Science Buddies

My daughter is in 3rd grade and working on her first science project. The question she came up with is how much electricity runs through potatoes, apples, lemons, and tomatoes? We need some help figuring out what might be our dependent variables and would a good hypothesis be stating which one you feel will yield the highest voltage? We are going to hook them all up to a voltmeter to see which one puts out the highest voltage. We found our real world application for the project is to use these as batteries. Any help with this would be greatly appreciated.

Thank you,

Hi Charity - Thank you for visiting the Science Buddies blog. There are a number of examples in the blog entry you were looking at, and I hope those gave you and your daughter a look at the standard way a hypothesis is written:

If I do __x__, then __y__ will happen.

We have developed the Ask an Expert Forum for exactly these types of questions. The Ask an Expert Forum is an online discussion board at Science Buddies staffed by volunteer scientists who respond to students’ science questions.

To register for a free Ask an Expert account, visit: http://www.sciencebuddies.org/science-fair-projects/phpBB3/index.php

Good luck with the project!

~Science Buddies

I am having trouble coming up with a hypotheses for a&P class my teacher said I could do it on anything.I'm am thinking of comparing ee shirt to a black tee shirt to see which is hotter and how much hotter. Is this a good hypotheses?.....12th grade....any ideas?

Hi Judy - Your hypothesis needs to clearly state what you think will happen in the form of:

"If I do _x_, then _y_ will happen."

Here are some resources on the Science Buddies site that may help:


If you need help as you work on your assignment or on the project, you can get assistance at the Ask an Expert forums. They can't write the hypothesis for you, but they can offer input and guidance as you work on it. http://www.sciencebuddies.org/science-fair-projects/phpBB3/index.php

Good luck with the project!

~ Science Buddies

I'm doing a science project from your website(which i love). Its the one about the Alka- Seltzer and the reaction time. Its called Plop,Plop,Fizz Fast. This is my hypothesis so far: When I modify the temperature of water, it will alter the reaction time of the Alka-Seltzer tablet. Is this a strong hypothesis?? Please help me with this, I really want a "A".

Hi! That is a great project to work on! If you would like feedback on your hypothesis (or if you have other questions about the procedure as you go along), you can get free help in our Ask an Expert forums: http://www.sciencebuddies.org/science-fair-projects/phpBB3/ucp.php?mode=register

Good luck!

Science Buddies

Apple cider vinegar will be more effective in eliminating or decreasing bacterial growth on all the household surface samples

""My hypothesis is that the pinwheel will get the most power at a 90 degree angle than the other positions. I hypothesize this because the wind will blow on the open spot of the pinwheel which will make the pinwheel turn faster.""
Is thiss a good hypothesis??

This my first science fair and I can't think of a good hypothesis (my science project is Finding the center of the milky way using globular star clusters)

Hi Charles - Figuring out what "question" you are asking in the project will help. You then will decide what you "think" the answer will be -- before you do the experiment.

You can find additional information on writing the hypothesis here:

After you write your hypothesis, you may find it helpful to use our free Ask an Expert forums to get input from our team of Experts.

Good luck!

I'm a Biology teacher and I found this website to be an excellent choice to use with my students. Thanks so much!

I'm in year 7 and i have to write a hypothesis on: "Do jelly crystals dissolve quicker in hot water" i have no idea where to start! Can you help me??

Writing your hypothesis is an important step of your science project. After reading the background material and carefully reviewing the procedure you will be using, what do you think will happen? The hypothesis will take the form of a statement that predicts what will happen to the dependent variable when the independent variable changes. If you click the "Project Guide" tab and select "Hypothesis" from the list, you will find resources and examples that may help you.

Something is wrong with this website everytime I search Steps of the Scientific Questions it allways says Scientific method and im only ten and need examples of questions of scienfific help me????!>!?!?!?!?!?!?!?!?!?!?!?!?!?!?!?!?!

Hi. You can view our resource on "Science Questions" by clicking the "Project Guide" tab on the Science Buddies site (above) and then clicking the "Your Question" link in the list. (It's near the top.)

Hi,Im doing my science project on "What is the point of boiling?" and I was wondering if this sounds like a good hypothesis? "If I put the water in/on an increasingly hot surface boiling will begin to happen."

Hi Alexandra - You may want to use our Ask an Expert forums to talk over your hypothesis and science project. Good luck!

Hi, does this sound like a good hypothesis?

Increasing the mass of an object will increase the frictional force it encounters.

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