The Speedy Oil Change Company advertised a 15-minute wait for anoil change. A sample of 23 oil changes showed a mean time of 13.5minutes and a standard deviation of 4.3 minutes. At the 5% level ofsignificance, is there evidence that the mean time for an oilchange is less than 15 minutes? Assume the population isapproximately normal.

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To test whether there is evidence that the mean time for an oil change is less than 15 minutes we ca... View the full answer