Although the slope does not measure association, it is useful for comparing effects for two variables that have the same units. For the Internet Use data file of 32 nations on the book’s website, let x = GDP (thousands of dollars per capita). For predicting y = percentage of adults using the Internet, the prediction equation is ŷ = 34.8 + 1.02x. For predicting y = percentage of adults using Facebook, the prediction equation is ŷ = 23.0 + 0.46x.
a. Explain how to interpret the two slopes.
b. For these nations, explain why a one-unit increase in GDP has a slightly greater impact on the percentage using the Internet than on the percentage using Facebook.