A researcher tested the effect of caffeine on sleep. Forty students volunteered to participate in the study and signed up for one of two nights. Students on Tuesday night drank a cup of regular coffee and students on Wednesday night received a cup of de-caff coffee. Students then took a nap and length of time to fall asleep was recorded with the aid of an EEG. Students in the caffeine group on average took 45 minutes to fall asleep where the students in the de-caff group on average took 10 minutes to fall asleep.

What is the problem of the experiment above?

What is the independent variable, dependent variable, and control group in the experiment?

What is the conclusion of the experiment?​