1. A company knows from their records that the mean dollar amount spent by customers in each store visit is $22.34, with a standard deviation of 14.06. They put on a promotion, mailing coupon booklets to a sample of known customers. After 2 weeks, the mean dollar amount spent by any customer redeeming a coupon (n=132) is calculated as $26.97.
a. Test if the promotion has been successful (i.e. has raised the mean spending of the target customers).
b. Give a 90% confidence interval for the mean spending of customers receiving the promotion.