12.1.

(a) Items are produced in such a manner that 2 percent turn out to be defective. A large number of such items, say n, are inspected and the relative frequency of defec- tives, say fp, is recorded. How large should n be in order that the probability is at least 0.98 that fp differs from 0.02 by less than 0.05?

(b) Answer

(a) above if 0.02, the probability of obtaining a defective item, is replaced by p which is assumed to be unknown.