Question: 73. The market research director for Dotty’s Department store wants to study women’s spending on cosmetics. A survey of the store’s credit card holders is designed in order to estimate the proportion of women who purchase their cosmetic primarily from Dotty’s Department Store and the mean yearly amount that women spend in cosmetics. From a previous survey, it was found that the standard deviation is approximately $18.

(a) What sample size is needed to have 99% confidence of estimating the mean within $5?

(b) What sample size is needed to have 90% confidence of estimating the mean within $0.045?

(c) Based on the (a) and (b) how many cardholders should be sampled?