The relationship between students' weights and earnings was explored. Because gender would play a role in both variables' values, regression was performed separately for males and females. Still, a positive correlation was found.
a. What additional confounding variable is the best explanation for the positive correlation?
b. If the interplay among weight, earnings, and age were explored, what role would weight play-explanatory or response?
c. If the interplay among weight, earnings, and age were explored, what role would earnings play-explanatory or response?
d. If the interplay among weight, earnings, and age were explored, what role would age play-explanatory or response?