1. Citibank Visa gives its cardholders "bonus dollars," which may be spent in partial payment for gifts purchased with the Visa card. The company wants to esti- mate the average amount of bonus dollars that will be spent by a cardholder enrolled in the program during a year. A trial run of the program with a random sample of 225 cardholders is carried out. The results are x = $259.60 and s = $52.00. Give a 95% con?dence interval for the average amount of bonus dollars that will be spent by a cardholder during the year.
2. An accountant wants to estimate the average amount of an account of a ser- vice company. A random sample of 46 accounts yields x = $16.50 and s = $2.20. Give a 95% con?dence interval for the average amount of an account.