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.
The manager notices that 20 minutes wait time (company policy) is not included and would like to have a 99% confidence interval that is wider than the currently obtained, the manager should

Question

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.  
 The manager notices that 20 minutes wait time (company policy) is not included and would like to have a 99% confidence interval that is wider than the currently obtained, the manager should

Accepted Answer

use fewer customers wait time in the sample.

Answer

select a different random sample of 150 customers wait time.

Answer

there is no way to increase the width of a 99% confidence interval as it is already the highest confidence level.

Answer

select more customers wait time for the sample.

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The amount of time customers at a “Quick-Change” motor oil store spend waiting ...

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