In the experiment about music and studying, what would you call the group of people that listen to classical music while studying?

experimental group

Explanation:

In an experimental study, at least two groups are compared to each other with respect to one independent variable: the experimental group and control group. Two groups are similar in every aspect except one that is the independent variable. The experimental group is the group for which the independent variable changes while it remains unchanged or constant for the control group. In this example, the independent variable is music. So experimental group is exposed to listening to music while studying. Members of the control group study without listening to any kind of music.  

the answer to your question is,

old stone age.

-mabel < 3

answer; the cats meowing will temporarily increase, but then it will decrease;