a) P(pregnant and test positive) = P(test positive | pregnant) *
P(pregnant)
                                                 Â
= 0.95 * 0.50 = 0.475
b) P(Positive test) = P(positive | pregnant) * P(pregnant) +
P(positive | not pregnant) * P(not pregnant)
                           Â
= 0.95 * 0.50 + 0.02 * (1 - 0.50)
                           Â
= 0.485
c) P(pregnant | positive) = P(positive | pregnant) *
P(pregnant)/P(positive)
                                    Â
= (0.95 * 0.50)/0.485
                                    Â
= 0.9794