Question

Suppose that 4% of all books in a library have red covers. In a group of n books selected from the shelves, consider the probability that at most two red books are selected. How large must n be before this probability is less than 0.02?

Answer 1

p = 0.04

The probability that at most two red books are selected. =

critical z value corresponding to probability 0.02 is -2.0537

let

solving for x we get two roots

and

sample size should be positive so we will consider x = 13.71

n shall be 188