Statistics - P-value Concept Approach

The Speedy Oil Change Company advertised a 15-minute wait for an oil change. A sample of 23 oil changes showed a mean time of 16.5 minutes and a standard deviation of 4.3 minutes. At the 5% level of significance, is there evidence that the mean time for an oil change is different from 15 minutes? Assume the population is approximately normal. Use the p-value approach.

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...freedom = 23 - 1 = 22

Decision Rule: Reject H0 if the test p- value < 0.05

t = (x-bar - ...