Question: For each of the following, explain whether the study summary describes an interacting variable or a confounding variable.

a. A comparison of the mean grade point averages of male and female students finds more difference for fraternity and sorority members than for students who are not fraternity and sorority members.

b. A study finds that wine drinkers tend to have better health than beer drinkers but also finds that wine drinkers tend to smoke less than beer drinkers.

c. It is found that drawing a happy face on a restaurant bill increases the mean tip percentage for female servers but does not increase the mean tip percentage for male servers.