A Researcher Studies the Effect of Exercise on Stamina

Multiple Choice

A researcher studies the effect of exercise on stamina. Participants are randomly assigned to be in an exercise or no-exercise group for 12 weeks. Stamina is then measured by how long participants can walk comfortably on a treadmill. In this study, the dependent variable is

A) the number of minutes participants spend comfortably on the treadmill.
B) whether the participants are in the exercise program or not.
C) the heart rate during the exercise program.
D) whether the duration of the exercise program is 12 weeks or longer.