The Solomon four-group design is a research design that attempts to take into account the influence of pretesting on subsequent posttest results. Some research designs include a pretest, which is taken before exposure to a treatment, and a posttest, which is administered after exposure to a treatment. Researchers employ a pretest-posttest design in order to demonstrate that exposure to a treatment led to differences between the pretest and posttest scores. However, there can be some drawbacks to including both a pretest and posttest in an experimental design. In particular, researchers have noted that including a pretest in a study design introduces threats to both internal and external validity. The Solomon four-group design employs a combination of pretest–posttest design and posttest-only design to combat ...