Answer:
In the study described, the independent variable is listening to music while falling asleep.
Explanation:
A dependent variable is what is being measured by the study. In this case, it is how long people sleep. The independent variable is the factor controlled or changed with the purpose of affecting the dependent variable. In Yolanda's study, it is the act of listening to music while falling asleep. Yolanda wants to see if listening to music will affect how long people sleep. To find out if it does, she divides participants into two groups - one that will and one that will not listen to music for 30 minutes before falling asleep.