For each pair of variables in I, II, III, and IV, indicate the shape of the curve that correctly depicts the relationship between the two variables. Choose from the following shapes:

a. Upward-sloping

b. Downward-sloping

c. Horizontal

d. Vertical

e. U-shaped

Assume that the first variable is measured on the horizontal axis of a graph and the second variable is measured on the vertical axis.

I. The temperature outside; the number of iced drinks you consume per day

II. The temperature outside; the number of letters in the alphabet

III. The number of times you brush your teeth per week; the number of cavities you’ll have at your next dental checkup

IV. Your age; the number of seconds it takes you to run 100 yards