Exercise 15

Suppose you buy a new car whose advertised gas mileage is 25 mpg (miles per gallon). After driving the car for several months, you find that you are getting only 21.4 mpg. You phone the manufacturer and learn that the standard deviation of gas mileage for cars of that model is 1.15 mpg.

1. Find the Z-score for the gas mileage of your car.

2. Does it appear that your car is getting unusually low gas mileage? Explain your answer using your Z-score.