With a Review of Identifying Variables Writing Hypotheses With a Review of Identifying Variables

Identifying Variables Review Independent 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 Variables Do 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 Variables Do tomato plants raised with music grow more tomatoes? Independent Variable: presence of music Dependent Variable: number of tomatoes grown

Practice Identifying Variables Does regular exercise decrease the number of colds a person becomes infected with? Independent Variable: frequency of exercise Dependent Variable: number of infections with cold virus

Hypothesis Statements You 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: Maybe Probably Might

Writing a Hypothesis A 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 Hypothesis Simply 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 Statement Research Question: What effect does the amount of light have on plant growth? Independent Variable: amount of light Dependent Variable: plant growth (height) If the amount of light shined on a plant each day increases, then the daily plant growth increases.

Example Hypothesis Statement Research Question: What effect does sleep have on test scores? Independent Variable: amount of sleep Dependent Variable: test scores If the amount of sleep a student gets decreases, then the average test score the student earns decreases.

Example Hypothesis Statement Research Question: What effect does batting practice have on a player’s batting average? Independent Variable: batting practice Dependent 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