EPA mpg. In 2008, the EPA revised their methods for estimating the fuel efficiency (mpg) of cars—a factor that plays an increasingly important role in car sales. How do the new highway and city estimated mpg values relate to each other? Here’s a scatterplot for 83 family sedans as reported by the U.S. government. These are the same cars as in Exercise 41 except that the Toyota Prius has been removed from the data and two other hybrids, the Nissan Altima and Toyota Camry, are included in the data (and are the cars with highest city mpg).

a) The correlation of these two variables is 0.823. Describe the association.

b) If the two hybrids were removed from the data, would you expect the correlation to increase, decrease, or stay the same? Try it using technology. Report and discuss what you find.

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+ 35 30 30 25 City mpg 20 20 15 0000 0000 24 27 30 33 Highway mpg