In a pretest/posttest research design, what does the researcher do?

In a pretest/posttest research design, the researcher measures a variable both before and after the manipulation of the independent variable. This approach allows for a clear comparison of the results to determine the effect of the intervention or treatment being tested. By establishing a baseline measurement (the pretest), the researcher can assess any changes that occur following the manipulation (the posttest). This design is particularly effective for demonstrating causal relationships, as it highlights the impact of the independent variable on the dependent variable over time.

The ability to compare pretest and posttest measurements enhances the validity of the findings by showing whether observed changes can be attributed to the manipulation rather than external factors. This dual measurement points to any differences that might arise, providing a thorough understanding of the intervention's effectiveness.