1. In which of the following scenario is it NOT appropriate to use a within-subjects design.
   1. A sports psychologist is interested in changes in athletic performance before and after an athlete listens to upbeat music.
   2. A researcher aims to compare exam improvement scores between a group of students who receive specific feedback and a group of students who receive general feedback.
   3. A researcher wonders if the attention span of students from an online course differs across time of study (daytime versus nighttime).