What is a repeated measures design primarily used to investigate?

A repeated measures design is primarily used to investigate the same group of participants under multiple conditions. This design allows researchers to observe how different conditions or treatments affect the same individuals, facilitating direct comparisons within the same subjects.

By using the same participants across various conditions, researchers can control for individual differences such as personality traits, intelligence, or prior experience, which might otherwise influence the results if different groups were used. Thus, this design enhances the sensitivity of the experiment to detect changes or effects resulting from the independent variable being tested.

In this context, the repeated measures design is particularly useful in studies where researchers want to assess changes in behavior or responses in relation to different conditions while minimizing variability that could arise from using different groups of participants. This leads to more reliable and valid results regarding the effects of the independent variable being researched.