Pre-Posttest With Control Group and Random Assignment (Experimental)

A study that involves measurements taken before and after the prevention intervention, and which includes a control group (that does not receive the prevention intervention) and an intervention group, both of which are randomly assigned, can simply be called an experimental research design.

Studies with experimental design assert the greatest degree of control over the major factors that influence the validity of results. As a result, the results obtained from these studies typically yield the most interpretable, definitive, and defensible evidence of prevention program effectiveness.

There are variations among experimental design studies, including randomized pretest and posttest studies with a control group, community randomized trials, and clinical randomized trials. Randomization is the best method to control for the major threats to validity. If the numbers of confirmed participants are large (such as 100 to 200), then simple random assignment may be adequate to establish equivalent groups. To achieve greater precision, stratified randomization may be used, in which individuals with selected demographic characteristics are grouped by a given characteristic (such as age or sex), paired with another individual or similar characteristic, and then each randomly assigned to an intervention or control group