Directly vary a condition you think might cause changes in behavior. These two groups should be exactly alike except for the condition you are varying. Record whether varying the condition has any effect on the behavior. Both groups are treated exactly the same except for the one condition you are intentionally varying. Then, we would test their driving ability on a driving simulator.
Independent variables are conditions varied or altered by the experimenter.
The size, amount, or value of an independent variable is set by the experimenter. Independent variables are suspected causes of differences in behavior. The amount is controlled by the experimenter and it is suspected to be the cause of deterioration of driving ability. Dependent variables measure the results of the experiment. Dependent variables reveal the effects that independent variables have on behavior.