Hypothesis Essay

Step 5: Hypothesis Statement

Hypothesis Statement

(will be worked on in class prior to due date)

Your hypothesis statement will be turned in during science class, reviewed by the teacher and returned. Below is a short explanation of a hypothesis statement and some examples of hypothesis statements.

Hypothesis statement--a prediction that can be tested or an educated guess.

In a hypothesis statement, students make a prediction about what they think will happen or is happening in their experiment. They try to answer their question or problem.


Question: Why do leaves change colors in the fall?

Hypothesis: I think that leaves change colors in the fall because they are not being exposed to as much sunlight.

Hypothesis: Bacterial growth may be affected by temperature.

Hypothesis: Chocolate may cause pimples


All of these are examples of hypotheses because they use the tentative word "may." However, their form in not particularly useful. Using the word does not suggest how you would go about proving it. If these statements had not been written carefully, they may not have been a hypotheses at all.

A better way to write a hypotheses is to use a formalized hypotheses

Example: If skin cancer is related to ultraviolet light, then people with a high exposure to uv light will have a higher frequency of skin cancer.

Example: If leaf color change is related to temperature, then exposing plants to low temperatures will result in changes in leaf color.

Example: If the rate of photosynthesis is related to wave lengths of light, then exposing a plant to different colors of light will produce different amounts of oxygen.

Example: If the volume of a gas is related to temperature, then increasing the temperature will increase the volume.

These examples contain the words, if and then. Formalized hypotheses contain two variables. One is "independent" and the other is "dependent." The independent variable is the one you, the scientist control and the dependent variable is the one that you observe and/or measure the results.

The ultimate value of a formalized hypotheses is it forces us to think about what results we should look for in an experiment.

Example: If the diffusion rate (dependent variable) through a membrane is related to molecular size (independent variable), then the smaller the molecule the faster it will pass through the membrane.




Both the hypothesis statement and the thesis statement answer a research question. 

  • A hypothesis is a statement that can be proved or disproved. It is typically used in quantitative research and predicts the relationship between variables.
  • A thesis statement is a short, direct sentence that summarizes the main point or claim of an essay or research paper. It is seen in quantitative, qualitative, and mixed methods research. A thesis statement is developed, supported, and explained in the body of the essay or research report by means of examples and evidence.

Every research study should contain a concise and well-written thesis statement. If the intent of the study is to prove/disprove something, that research report will also contain a hypothesis statement.

NOTE: In some disciplines, the hypothesis is referred to as a thesis statement! This is not accurate but within those disciplines it is understood that "a short, direct sentence that summarizes the main point" will be included.

For more information, see The Research Question and Hypothesis (.doc file from the English Language Support, Department of Student Services, Ryerson University).

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