Mr. Good Wrench advertises that a customer will have to wait no more than 30 minutes for an oil change. A sample of 26 oil changes had a standard deviation of 4.8 minutes. Use this information to calculate a 90% confidence interval for the population standard deviation waiting time for an oil change.

The 90% confidence interval for the population standard deviation waiting time for an oil change is (3.9, 6.3).

Step-by-step explanation:

The (1 - α)% confidence interval for the population standard deviation is:

The information provided is:

n = 26

s = 4.8 minutes

Confidence level = 90%

Compute the critical values of Chi-square as follows:

*Use a Chi-square table.

Compute the 90% confidence interval for the population standard deviation waiting time for an oil change as follows:

Thus, the 90% confidence interval for the population standard deviation waiting time for an oil change is (3.9, 6.3).

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step-by-step explanation:

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