an auto make 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 the standard deviation of 5 miles per gallon. at alpha=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 population is normally distributed