In a Study on Sleep Habits, It Was Found That

Short Answer

In a study on sleep habits, it was found that college students who got at least 7 hours of sleep the night before a test performed better on exams than college students who got less than 7 hours of sleep.
-In the following diagram, fill in the blanks to describe a potential confounding variable in this study.
Drop-down menu for (1) and (2):
•Enrolled in more credit hours
•Enrolled in less credit hours
•Perform better on exams
•Perform worse on exams