The Solomon four-group design is a true experimental design that specifically controls for the effects of taking a pretest. It involves four groups: two that receive a pretest and two that do not. This setup allows researchers to determine if the pretest itself has an effect on the outcomes, increasing internal validity. “The Solomon four-group design is the only experimental design that controls for both the effects of pretesting and treatment.”
[Reference: Helwig, A. A. (2020). CPCE Study Guide and Review; Royse, D., Thyer, B. A., & Padgett, D. K. (2016). Program Evaluation: An Introduction.]
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