What distinguishes a pre-test and post-test design?

A pre-test and post-test design is characterized by the measurement of participants' outcomes before and after an intervention. This design allows researchers to assess how the intervention has impacted the participants over time. By gathering data at both stages, the researcher can make comparisons and identify any changes that may have resulted from the intervention. For instance, if a study is evaluating the effectiveness of a new teaching method, measuring students' knowledge before and after the method is implemented provides a clear picture of its effectiveness.

The other options do not accurately describe the pre-test and post-test design. Measurement taken only after the intervention does not allow for an assessment of change, which is the fundamental purpose of this design. While control groups can be a part of a broader research design, the focus of this specific design is on measuring the same group before and after the treatment, rather than restricting measurement to only control groups. Lastly, a focus on qualitative data is not a defining feature of this design, which can be applied to both quantitative and qualitative outcomes. Thus, the correct understanding emphasizes the importance of measuring both before and after to draw meaningful conclusions regarding the effects of an intervention.