A direct-mail sales company should find out its credit policies quite carefully. Assume that the firm suspects that advertisements in a certain magazine have led to the excessively high rate of write-offs (accounts regarded as uncollectible). The firm desires to establish 90% confidence interval for this magazine's write-off proportion that is accurate to 0.02 (margin of error=.02)
a) How many accounts should be sampled to guarantee this goal?