In an experiment, a scientist decides to study the effect of exercise on cholesterol levels in people. He studies two set of people—those who exercise every day for an hour and those who don’t exercise at all. In this case, the statement that people who exercise for an hour may have lower cholesterol levels is (blank). To test this statement, the scientist would measure cholesterol levels in exercisers and non-exercisers. The cholesterol levels would be (blank).