For each of the following scenarios, the researchers are interested in comparing the mean of a numerical variable measured in two circumstances. For each, say whether a paired t-test or two-sample t-test would be appropriate.

a. The weight of 14 patients before and after open-heart surgery.

b. The smoking rates of 14 men measured before and after a stroke.

c. The number of cigarettes smoked per day by 14 men who have had strokes compared with the number smoked by 14 men who have not had strokes.

d. The lead concentration upstream from five power plants compared with the levels downstream from the same plants.

e. The basal metabolic rate (BMR) of seven chimpanzees compared with the BMR of seven gorillas.

f. The photosynthetic rate of leaves in the crown of 10 Sitka spruce trees compared with the photosynthetic rate of leaves near the bottom of the same trees.

g. The photosynthetic rates of 10 randomly chosen Douglas-fir trees compared with 10 randomly chosen western red cedar trees.

h. The photosynthetic rate measured on 10 randomly chosen Sitka spruce trees compared with the rate measured on the western red cedar growing next to each of the Sitka spruce trees.