Pretest–Posttest Designs

The Pretest–Posttest Design in Evaluation

Despite its high susceptibility to threats of internal validity, the pretest–posttest design is commonly used across therapeutic and educational settings for several reasons. First, it is unethical to assign participants who need immediate treatment or intervention, such as clients with depressive symptoms or children having posttraumatic stress disorder, to a control group. Second, resources and manpower may not be sufficient to conduct sophisticated experimental studies. Third, teachers without advanced research training can use this design to evaluate their own practice within school settings. Finally, the design can be a cost-effective way to study the preliminary outcomes of a program and decide whether the research should be extended.

Similar to health services, program developers in education research may also use the pretest–posttest design to determine the effectiveness of an education intervention program. For example, the pretest–posttest design was used in the experimental implementation phase of a positive youth development project called Positive Adolescent Training through Holistic Social Programs (P.A.T.H.S.) before a randomized group trial was adopted in implementing the program across Hong Kong. In addition, the American Association of State Colleges and Universities has suggested using the pretest–posttest design as a value-added measure in evaluating student learning and adjusting course curricula to better satisfy students’ needs. Typically, a pretest is given to students at the beginning of a course to determine their initial understanding of the measures stated in the learning objectives, and posttest is conducted just after completion of the course to determine what the students have learned. Ideally, there will be a positive change in outcomes.

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