1. Variable = anything that can change or vary in an experiment.

2. Independent Variable (IV)
A factor changed on purpose by the experimenter.
Also known as a manipulated variable (MV).
Levels of IV are ways the experimenter changes the IV.

3. Example
A Nike scientist wants to test the thickness of the soles in running shoes on the speed of an Olympic runner.
What is the IV?
Her Levels of IV are:
0.5 cm thick
1.0 cm thick
1.5 cm thick
2.0 cm thick
2.5 cm thick

4. Dependent Variable (DV)
A factor that changes because of the IV
Also known as the responding variable (RV)
The DV is what the experimenter will measure and record.

5. So the thickness of the shoe soles is the IV.
What is the DV?
The speed of the runner is the DV.

6. Constants The factors that are kept the same in an experiment.
The more constants in an experiment, the better to determine the effect of the IV.

7. Would the Nike scientist want to use two different runners?

8. What are some other factors the scientist would want to keep constant?