To test the effectiveness of a job training program on the subsequent wages of workers, we specify the model log1wage2 5 b0 1 b1train 1 b2educ 1 b3exper 1 u, where train is a binary variable equal to unity if a worker participated in the program. Think of the error term u as containing unobserved worker ability. If less able workers have a greater chance of being selected for the program, and you use an OLS analysis, what can you say about the likely bias in the OLS estimator of b1? (Hint: Refer back to Chapter 3.)