Posted by **sue** on Tuesday, July 27, 2010 at 7:32pm.

A car company says that the mean gas mileage for its luxury sedan is at least 21 miles per gallon. You believe the claim is incorrect and find that a random sample of five cars has a mean gas mileage of 19 miles per gallon and a standard deviation of 4 miles per gallon. Assume the gas mileage of all of the company’s luxury sedans is normally distributed. At á = 0.05, test the company’s claim.

• What is the difference between a critical value and a test statistic?

• Decide whether you should use a normal sampling distribution or a t-sampling distribution to perform the hypothesis test.

• Why would you use a z-test rather than a t-test?

• Which do you think you will use more often? Justify your decisions.

• Then use the distribution to test the claim.

• Write a short paragraph about the results of the test and what you can conclude about the claim.

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