7.19 Fuel economy.

Although the Environmental Protection Agency (EPA) establishes the tests to determine the fuel economy of new cars, it often does not perform them. Instead, the test protocols are given to the car companies, and they perform the tests themselves. To keep the industry honest, the EPA does run some spot checks each year. Recently, the EPA announced that Hyundai and Kia must lower their fuel economy estimates for many of their models.⁸ Here are some city miles per gallon (mpg) values for one of the models the EPA investigated:

Give a 95% confidence interval for , the mean city mpg for this model.