Jennifer Wants to Study Motor-Pursuit Performance Tracking a Moving Light

Multiple Choice

Jennifer wants to study motor-pursuit performance tracking a moving light with a hand-held wand) under each of three conditions of distraction, high, medium, and low. Instead of using three separate groups of participants, she makes sure her groups are equivalent by testing the same 12 participants under all three conditions of distraction. She finds that performance is poorest in the first high distraction) condition, better in the second medium distraction) , but best in the third low distraction) condition. She concludes that performance is hindered by distraction. What is the problem with this interpretation?

A) her participants could have improved simply with practice over the three conditions
B) comparisons like that should only be made across separate groups of people
C) twelve participants are not enough to allow for such conclusions
D) you can't measure and compare a variable like motor pursuit performance over time