Pretest–Posttest Designs

In single-group pretest–posttest designs, or pretest–posttest designs, the dependent variable or variables are measured before the intervention (i.e., the pretest) and after the intervention (i.e., the posttest). Typically, measures used in the pretest and the posttest are the same, and changes in the dependent variable from pretest to posttest are interpreted to reflect the effectiveness of the intervention (the independent variable). This entry describes the pretest–posttest design compared with classical experimental designs, the role of the pretest–posttest design in human services and education evaluation, possible threats to the internal validity, issues related to the external validity, and ways to strengthen the design.

A pretest–posttest design is a form of pre-experimental design that does not have control or comparison groups. This is a major difference between pretest–posttest ...