Assume all people have black, brown, blond or red hair. Which of the following regressions immediately tells you whether redheads are smarter than the average non-redhead?
A. B0_hat + B1_hat*Red + u_hat
B. B0_hat + B1_hatRed + B2_hatBlond + u_hat
C. B0_hat + B1_hatRed + B2_hatBlack+ B3_hat*Brown +u_hat
D. B0_hat + B1_hatRed + B2_hatBlond+ B3_hatBlack + B4_hatBrown +u_hat
Answer: A. B0_hat + B1_hat*Red + u_hat