15.21 For each of the following, identify the independent variable(s), the dependent variable(s), and the level of measurement (nominal, ordinal, scale).

a. The number of loads of laundry washed per month was tracked for first-year students and seniors living in university dorms.

b. A researcher interested in people’s need to maintain their social image collected data on the number of kilometers on someone’s car and his or her rank for “need for approval” out of the 183 people studied.

c. A professor of social science was interested in whether involvement in campus life is significantly impacted by whether a student lives on or off campus. Thirty-seven students living on campus and 37 students living off campus were asked whether they were an active member of a club.