For Exercises 2.23 and 2.24, see page 75; and for 2.25 and 2.26, see pages 77–78.

Question 2.37

2.37 Fuel efficiency and CO2 emissions

In Example 2.7 (pages 70–71), we examined the relationship between highway MPG and CO2 emissions for 1067 vehicles for the model year 2014. Let's examine the relationship between the two measures of fuel efficiency in the data set, highway MPG and city MPG.

canfuel

  1. Make a scatterplot with city MPG on the x axis and highway MPG on the y axis.
  2. Describe the relationship.
  3. Calculate the correlation.
  4. Does this numerical summary give a good indication of the strength of the relationship between these two variables? Explain your answer.

2.37

(b) The relationship is somewhat linear but may also be slightly curved. Hwy MPG and City MPG increase together. (c) . (d) The correlation is a decent numerical summary because the data are somewhat linear, but a curve may provide a better description of the relationship.