A bank with a branch located in a commercial district of a city has the business objective of developing an improved process for serving customers during the noon-to- 1 P.M. lunch period. Management decides to first study the waiting time in the current process. The waiting time is defined as the time that elapses from when the customer enters the line until he or she reaches the teller window. Data are collected from a random sample of 15 customers, and the results (in minutes) are as follows (and stored in Bank 1):

Suppose that another branch, located in a residential area, is also concerned with improving the process of serving customers in the noon-to-1 P.M. lunch period. Data are collected from a random sample of 15 customers, and the results are as follows (and stored in Bank 2):

a. Assuming that the population variances from both banks are equal, is there evidence of a difference in the mean waiting time between the two branches? (Use α = 0.05.)
b. Determine the p-value in (a) and interpret its meaning.
c. In addition to equal variances, what other assumption is necessary in (a)?
d. Construct and interpret a 95% confidence interval estimate of the difference between the population means in the two branches.

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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 9.66 5.90 8.02 5.79 8.73 3.82 8.01 8.35 10.49 6.68 5.64 4.08 6.17 9.91 5.47