A well known bank credit card firm wishes to estimate the proportion of credit card holders who carry a nonzero balance at the end of the month and incur and interest charge. Assume that the desired margin of error is .03 at 98% confidence.
(a) How large a sample should be selected if it is anticipated that roughly 70% of the firm's card holders carry a non-zero balance at the end of the month?
(b) How large a sample should be selected if no planning value for the proportion could be specified?
Estimation of sample size based on proportion.