7. The values listed below are the waiting times (in minutes) of customers at the Jefferson Valley Bank, where customers enter a single waiting line that feeds three teller windows. Construct a 95% confidence interval for the population standard deviation and interpret the results.
8. The values listed below are the waiting times (in minutes) of customers at the Bank of Providence, where customers enter any one of three different lines that have formed at three teller windows. Construct a 95% confidence interval for the population standard deviation and interpret the results.
4.2 5.4 5.8 6.2 6.7 7.7 8.5 9.3 10.0
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9. Comparing the results from problems 7 and 8, do the confidence intervals suggest a difference in the variation among waiting times? Which arrangement seems better: the single-line or multiple-line?
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10. You want to estimate for the population of waiting times at a fast-food restaurant’s drive-up windows, and you want to be 95% confident that the sample standard deviation is within 20% of . Find the minimum sample size needed. Is this sample size practical?
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