How much more effective is exercise and drug treatment than drug treatment alone at reducing the rate of heart attacks among men aged 65 and older? To find out, researchers perform a completely randomized experiment involving 1000 healthy males in this age group. Half of the subjects are assigned to receive drug treatment only, while the other half are assigned to exercise regularly and to receive drug treatment. The most appropriate inference method for answering the original research question is

(a) one-sample z test for a proportion.

(b) two-sample z interval for p1 − p2.

(c) two-sample z test for p1 − p2.

(d) two-sample t interval for m1 − m2.

(e) two-sample t test for m1 − m2.