Suppose 84% of hypertensives and 23% of normotensives are classified as hypertensive by an automated blood-pressure machine. What is the PV+ of the machine, assuming 20% of the adult population is hypertensive? Solution Let H = hypertensive N = normotensive P = positive for hypertension Hence, P(H|P) = P(H) P(P|H) / P(P) However, P(P) = P(H) P(P|H) + P(N) P(P|N) P(P) = 0.20*0.84 + (1-0.20)*0.23 = 0.352 THus, P(H|P) = PV+ = 0.20*0.84/0.352 = 0.477272727 [ANSWER].