An automotive engineer believes that her newly designed engine will be a great gas saver. A large number of tests on engines of the old design yielded a mean gasoline consumption of 27.5 miles per gallon, with a standard deviation of 5.2. Fifteen new engines are tested. The mean gasoline consumption for the new engine is 29.6 miles per gallon. a. What is the directional alternative hypothesis? b. What is the null hypothesis? c. What is your obtained z-score? d. What do you conclude?

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