Waiting in Line The Jefferson Valley Bank once had a separate customer waiting line at each teller window, but it now has a single waiting line that feeds the teller windows as vacancies occur. The standard deviation of customer waiting times with the old multipleline configuration was 1.8 min. Listed below is a simple random sample of waiting times

(minutes) with the single waiting line. The 10 sample values have a standard deviation of 0.5 min.

a. When the bank changed from multiple waiting lines to a single line, how was the mean waiting time affected?

6.5 6.6 6.7 6.8 7.1 7.3 7.4 7.7 7.7 7.7

b. When the bank changed from multiple waiting lines to a single line, how was the variation among waiting times affected?

c. What improvement occurred with the change from multiple waiting lines to a single line?

d. What procedure can be used to determine that the single waiting line is better?