Joe Jobs is a VP of a very large international company. Joe wants to estimate the mean age of the customers that purchase products from the company. He plans to use a sample of customers to estimate the mean and wants to be 95% confident that the maximum error in his estimate is one year. From a previous survey, he is able to determine that the standard deviation of ages is 6. Calculate the sample size Joe needs in order to estimate the mean age of the customers given the above parameters.

9.

Mary Sales owns a large retail sales company. She wants to estimate the mean amount the customers spend with a visit to one of her stores. Mary wants to be 99% confident that the maximum error in her estimate is $5. From a previous estimate she has a standard deviation of sales of $20. Using the information above determine the appropriate sample size to make the estimate.