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 multiple-line 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?
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b. When the bank changed frommultiple 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?