The group in research that differs from the experimental group only in that the latter receives the positive manipulation pertaining to the independent variable. A control group is necessary to infer that the changes observed in the experimental group are the result of the independent variable. For example, if a researcher wished to know the effects of the drug diazapam (independent variable) on electrodermal responses (dependent variable), the group that did not receive the medication would be called the control group and the medicated group would be the experimental group.