A bank with the branch situated in the commercial district of city has the business objective of developing an enhanced process for serving customers throughout the noon-to- 1 P.M. lunch period. Management decides to first study the waiting time in current procedure. The waiting time is stated as the time that elapses from when the customer enters the line till he or she reaches the teller window. Data are gathered from the random sample of 15 customers, and the results (in minutes) are as follows (and stored in bank 1):
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
Assume that another branch, situated in a residential area, is as well concerned with enhancing the procedure of serving customers in the noon-to-1 P.M. lunch period. Data are gathered from a random sample of 15 customers, and the results are as follows (and stored in bank 2):
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
a. Supposing 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.)
c. In addition to equal variances, what other statement is necessary in (a)?