Final answer:
The independent variable is Jason studying for the test, the dependent variable is the test scores, and the control variable is the absence of studying by Stacy.
Step-by-step explanation:
In the given study scenario, the independent variable is the act of Jason studying for the test, as it is manipulated by Jason himself. The dependent variable is the test scores, as they are measured to see the effect of studying. The control variable is the absence of studying by Stacy, as it is kept constant to compare the effects of studying.