Chapter 9, Problem 74PS

A bank branch located in a commercial district of a city has the business objective of improving the process for serving customer during the noon-to-1:00 p.m. lunch period. The waiting time (defined as the time the customer enters the line until he or she reaches the teller window) of a random sample of 15 customers is collected, and the results are organized and stored in Bank1. These data are:

a. At the 0.05 level of significance, is there evidence that the population mean waiting time is less than 5 minutes?

b. What assumption about the population distribution is needed in order to conduct the t test in (a)?

c. Construct a boxplot or a normal probability plot to evaluate the assumption made in (b).

d. Do you think that the assumption needed in order to conduct the t test in (a) is valid? Explain.

e. As a customer walks into the branch office during the lunch hour, she asks the branch manager how long can expect to wait. The branch manager replies, “Almost certainly not longer than 5 minutes. “On the basis of the results of (a), evaluate this statement.