9. An automobile manufacturer who wishes to advertise that one of its models achieves 30 mpg (miles per gallon) decides to carry out a fuel efficiency test. Six nonprofessional drivers are selected, and each one drives a car from Phoenix to Los Angeles. The resulting fuel efficiencies (in miles per gallon) are: 27.2, 29.3, 31.2, 28.4, 30.3, and 29.6. Assuming that fuel efficiency is normally distributed under these Circumstances with standard deviation O = 1.408, do the data contradict the claim that true average fuel efficiency is (at least) 30 mpg? Use a = 0.05. [Hint: Use the Z-test for the population mean ( ] a. Hypotheses: b. Calculations: Test Statistics