A bank branch located in a commercial district of a city has the business objective of improving the 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 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 pop-ulation 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 she can expect to wait. The branch manager replies, €œ Almost certainly not longer than 5 minutes.€ On the basis of the results of (a), evaluate this statement.

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4.21 5.55 3.02 5.13 4.77 2.34 3.54 3.20 4.50 6.10 0.38 5.12 6.46 6.19 3.79