Question: An automaker estimates that the mean gas mileage of its luxury sedan is at least 25 miles per gallon. A random sample of eight such cars had a mean of 23 miles per gallon and a standard deviation of 5 miles per gallon. At a = 0.05, can you reject the auto maker’s claim that the mean gas mileage of its luxury sedan is at least 25 miles per gallon? Assume the population is normally distributed.

a. (4) Write Ho and Ha:

b. (8) Determine whether the hypothesis test is a one-tailed or a two-tailed test and

whether to use a z-test or a t-test:

c. (8) Find the critical value and identify the rejection region.

d. (8) Calculate the test statistic.

e. (12) Decide whether to reject or fail to reject the null hypothesis. Interpret the

decision in the context of the original claim.