The Environmental Protection Agency (EPA) tests all new cars and provides a mileage rating for both city and highway driving conditions. For 2015, 32 electric cars were tested, and the data are contained in the data file Electric Cars (source: www.fueleconomy.gov). In this exercise, focus on the city and highway mileage data.

a. Calculate the sample mean miles per gallon (mpg)

for both city and highway driving for the cars. Also calculate the sample standard deviation for the two mileage variables. Do the data tend to support the premise that cars get better mileage on the highway than around town? Discuss.

b. Referring to part

a, what can the EPA conclude about the relative variability between car models for highway versus city driving? (Hint: Compute the appropriate measure to compare relative variability.)