Question

A survey of the mean number of cents off that coupons give was conducted by randomly surveying one coupon per page from the coupon sections of a recent Rockford newspaper. The following data were collected: 20¢; 75¢; 50¢; 75¢; 30¢; 55¢; 10¢; 40¢; 30¢; 55¢; $1.50; 40¢; 65¢; 40¢. Assume the underlying distribution is approximately normal. Construct a 95% confidence interval for the population mean worth of coupons. Find the upper limit of the confidence interval. Enter it rounded to the nearest cent (2 decimal places)

Answer 1

Now ,

Given : n=14 , ,

The sample mean is ,

The sample standard deviation is  

The critical value is ,

; From t-table

Therefore , the 95% confidence interval for the population mean worth of coupons is ,

Therefore , the upper linit of the confidence interval is 72.14