An experiment randomly assigns 100 subjects suffering from high cholesterol to one of four groups: low-dose Lipitor, high-dose Lipitor, low-dose Zocor, high-dose Zocor. After three months of treatment, the change in cholesterol level is measured.
a. Identify the response variable and the two factors.
b. What are four treatments that can be compared with this experiment?
c. What comparisons are relevant when we control for dose level?