Writing HypothesesWith a Review of Identifying Variables

Identifying Variables ReviewIndependent Variable – the variable that the

scientist will change to observe the effect

Dependent Variable – the variable that the scientist will measure and record - It’s the data of the experiment

Controlled – the variable(s) that the scientist purposely keeps the same

Practice Identifying VariablesDo people that use cell phones while driving

have more automobile accidents?

Independent Variable: use of cell phones while driving

Dependent Variable: number of automobile accidents

Practice Identifying VariablesDo tomato plants raised with music grow more

tomatoes?

Independent Variable: presence of musicDependent Variable: number of tomatoes

grown

Practice Identifying VariablesDoes regular exercise decrease the number of

colds a person becomes infected with?

Independent Variable: frequency of exerciseDependent Variable: number of infections

with cold virus

Hypothesis StatementsYou will need to write a hypothesis

statement any time you plan to test how two variables are related (ie. conduct

an experiment). But what is a hypothesis?

What is a hypothesis?A statement that predicts something

Must be testable and measureable

Written as an “if” “then” statement

A Hypothesis is NOT…A question

A statement that uses words like:MaybeProbablyMight

Writing a HypothesisA hypothesis simply combines the

independent and dependent variables into a prediction statement.If you know the independent and dependent

variables, writing a hypothesis statement is easy!

Writing a HypothesisSimply insert the independent and dependent

variables into the following format:If the _______IV_______ increases/decreases, then the _______DV_______ increases/decreases.

The independent variable is the “if” part of the hypothesis and the dependent variable is the “then” part.

Use only “increases” OR “decreases” for each part of your hypothesis statement.

Example Hypothesis StatementResearch Question: What effect does the

amount of light have on plant growth?

Independent Variable: amount of lightDependent Variable: plant growth (height)

If the amount of light shined on a plant each day increases, then the daily plant growth increases.

Example Hypothesis StatementResearch Question: What effect does sleep

have on test scores?

Independent Variable: amount of sleepDependent Variable: test scores

If the amount of sleep a student gets decreases, then the average test score the student earns decreases.

Example Hypothesis StatementResearch Question: What effect does batting

practice have on a player’s batting average?

Independent Variable: batting practiceDependent Variable: batting average

If the amount of batting practice increases, then the player’s batting average increases.

Time to Practice on Your Own!

Remember, identify the variables first, then plug the IV and DV into the hypothesis

statement format