When Testing the Perceptual Effects of Music Training, Why Should

Multiple Choice

When testing the perceptual effects of music training, why should a researcher use random assignment of participants to a musical group or control activity?

A) Participants are usually equally glad to be assigned to any kind of activity.
B) Otherwise, the direction of causation is questionable, since those in the music group may already have superior listening skills that made them more likely to want to play music.
C) Random assignment makes the music group more diverse.
D) Random assignment minimizes individual differences within each group, making the groups easier to reason about.