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The amount of time customers at a “Quick-Change” motor oil store spend waiting ...
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The amount of time customers at a “Quick-Change” motor oil store spend waiting for their cars to be serviced has the Normal distribution with mean μ and standard deviation σ = 4 minutes. It is company policy that the customer wait time should be 20 minutes (or less). The manager of a particular store selects a random sample of 150 customer wait times and observes a mean wait time of 21 minutes.
A 99% confidence interval for the population mean wait time μ based on this sample was calculated to be (20.16, 21.84) minutes. Suppose that the population standard deviation σ = 4 was wrong and the correct population standard deviation should be σ =5, a new 99% confidence interval for the same sample was calculated using σ = 5. The new 99% confidence interval