The market research director for Dotty's Department Store wants to study women's spending on cosmetics. A survey of the store's customers is designed in order to estimate the proportion of women who purchase their cosmetics primarily from Dotty's Departme

Question no 8.71

The market research director for Dotty's Department

Store wants to study women's spending on cosmetics. A

survey of the store's customers is designed in order to estimate

the proportion of women who purchase their cosmetics

primarily from Dotty's Department Store and the mean

yearly amount that women spend on cosmetics. A previous

survey found that the standard deviation of the amount

women spend on cosmetics in a year is approximately $18.

a. What sample size is needed to have 99% confidence of

estimating the population mean to within ± $5?

b. How many of the store's credit card holders need to be

selected to have 90