In an experiment, the control group describes the subjects that do not receive any treatment. Jackson defines the control as the group that “does not receive any level of the independent variable” given to the experimental group. It serves as the baseline against which the effects of the independent variable are measured.
Control is important in experiments, as it enables one to identify and separate variables of the study. It also helps reduce researcher bias by providing a standard. Since it is not possible to remove all extraneous variables, the use of controls enhances the statistical validity of a study. In single or multiple comparative studies, controls provide baseline data to compare the experimental results with and draw conclusions.
Normally, a random sample is drawn from the target population before selecting the control and experimental group subjects.