10.51 A credit bureau analysis of undergraduate students’

credit records found that the average number of credit cards in an undergraduate’s wallet was 4.09

(“Undergraduate Students and Credit Cards in 2004,”

Nellie Mae, May 2005). It was also reported that in a random sample of 132 undergraduates, the sample mean number of credit cards that the students said they carried was 2.6. The sample standard deviation was not reported, but for purposes of this exercise, suppose that it was 1.2. Is there convincing evidence that the mean number of credit cards that undergraduates report carrying is less than the credit bureau’s figure of 4.09? (Hint: See Example 10.14.)