A bank branch located in a commercial district of a city has developed an improved process for serving customers during the noon-to-1:00 p.m. lunch period. The waiting time (defined as the time the...

A bank branch located in a commercial district of a city has developed an improved process for serving customers 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 all customers during this hour is recorded over a period of 1 week. A random sample of 15 customers (see the data file bank1.xls) is selected, and the results are as follows:

a. At the 0.05 level of significance, is there evidence that the mean waiting time is less than 5 minutes? b. What assumption must hold in order to perform the test in (a)?

c. Evaluate the assumption in (b) through a graphical approach. Discuss.

d. As a customer walks into the branch office during the lunch hour, she asks the branch manager how long she 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.