Assume that each sample is obtained by randomly selecting values from a population with a normal distribution.
The listed values are waiting times (in minutes) of customers at the
Humber Valley Credit Union, where customers enter a single waiting line that feeds three windows. Construct a 95% confidence interval for the population standard deviation σ.
6.5 6.6 6.7 6.8 7.1 7.3 7.4 7.7 7.7 7.7
b. The listed values are waiting times (in minutes) of customers at the Durham Credit Union, where customers may enter any one of three different lines that have formed at three different teller windows. Construct a 95% confidence interval for cr.
4.2 5.4 5.8 6.2 6.7 7.7 7.7 8.5 9.3 10.0
c. Interpret the results found in (a) and (b). Do the confidence intervals suggest a difference in the variation among waiting times? Which arrangement seems better: the single-line system or the multiple-line system?