The variables y = annual income (thousands of dollars), x1 = number of years of education, and x2 = number of years experience in job are measured for all the employees having city-funded jobs in Knoxville, Tennessee. Suppose that the following regression equations and correlations apply:
(i) ŷ = 10 + 1.0x1, r = 0.30.
(ii) ŷ = 14 + 0.4x2, r = 0.60.
The correlation is −0.40 between x1 and x2. Which of the following statements are true?
a. The weakest association is between x1 and x2.
b. The regression equation using x2 to predict x1 has negative slope.
c. Each additional year on the job corresponds to a $400 increase in predicted income.
d. The predicted mean income for employees having 20 years of experience is $4000 higher than the predicted mean income for employees having 10 years of experience.