A researcher wants to see if a protein-enriched diet will enhance the maze-running performance of rats. One group of rats is fed the high-protein diet for the duration of the study; the other group continues to receive ordinary rat chow. In this experiment, the rats' maze-running performance is the

A) correlated variable.
B) control variable.
C) dependent variable.
D) independent variable.

The maze-running performance of rats is the variable being measured in the experiment, making it the dependent variable. The independent variable is the protein-enriched diet, which is being manipulated to see its effect on the dependent variable. The control variable would be any other factor that could affect the maze-running performance, such as the type of maze or the age of the rats, which would be standardized across both groups. The correlated variable would be a variable that is associated with both the independent and dependent variables but is not being directly examined in the experiment.