12.24 When can you compare slopes? Although the slope does not measure association, it is useful for comparing effects for two variables that have the same units. Let x = GDP (thousands of pounds per capita). For predicting y = consumer expenditure, the prediction equation is yn = 3034.89 + 0.52x. For predicting y = investment expenditure, the prediction equation is yn = 2037.73 + 0.27x.

a. Explain how to interpret the two slopes.

b. Explain why a one-unit increase in GDP has a slightly greater impact on consumer expenditure than on investment expenditure.