C6.9 The data set NBASAL.RAW contains salary information and career statistics 269 players in the National Basketball Association (NBA). Estimate a model relating points-per-game (points) to years in the league (exper), age, and years played in college (coll). Include a quadratic in exper; the other variables should appear in level form. Report the results in the usual way. (ii) Holding college years and age fixed, at what value of experience does the next year of experience actually reduce points-per-game? Does this make sense? (iii) Why do you think coll has a negative and statistically significant coeffi- cient? (Hint: NBA players can be drafted before finishing their college careers and even directly out of high school.) (iv) Add a quadratic in age to the equation. Is it needed? What does this appear to imply about the effects of age, once experience and education are con- trolled for? (v) Now regress log(wage) on points, exper, exper, age, and coll. Report the results in the usual format. (vi) Test whether age and coll are jointly significant in the regression from part (v). What does this imply about whether age and education have sep- arate effects on wage, once productivity and seniority are accounted for?