Which design samples behavior before and after treatment?

The pretest-posttest design is characterized by assessing the same participants before and after a specific treatment or intervention. This design allows researchers to determine any changes in behavior that may occur as a result of the treatment, as it provides a baseline measure (the pretest) to compare against the post-treatment measure (the posttest).

This design is particularly effective in evaluating the effectiveness of a treatment, as it facilitates direct comparisons within the same group of individuals over time. By focusing on the change from the pretest to the posttest, researchers can draw conclusions about the impact of the intervention on participants' behaviors, thereby establishing a causal relationship more confidently.

In contrast, other designs serve different purposes. For example, a random group design typically involves comparing different groups without repeated measures on the same participants; a repeated measures design focuses on assessing the same participants multiple times but does not necessarily involve a clear pretest and posttest structure aimed at measuring the intervention's effects. A reversal design requires conditions to be altered in a specific manner, often reverting to an initial phase after an intervention, rather than just comparing before and after treatment.