2.21 Fuel efficiency and CO_2 emissions

Refer to Example 2.7 (pages 70–71), where we examined the relationship between CO₂ emissions and highway MPG for 1067 vehicles for the model year 2014. In that example, we used MPG as the explanatory variable and CO₂ as the response variable. Let’s see if the relationship differs if we change our measure of fuel efficiency from highway MPG to city MPG. Make a scatterplot of the fuel efficiency for city driving, city MPG, versus CO₂ emissions. Write a summary describing the relationship between these two variables. Compare your summary with what we found in Example 2.7.