Introductory Econometrics 4th Edition by Jeffrey Wooldridge

Exercise 6

Use CRIME4.RAW for this exercise.
( i) Reestimate the unobserved effects model for crime in Example 13.9 but use fixed effects rather than differencing. Are there any notable sign or magnitude changes in the coefficients What about statistical significance
(ii) Add the logs of each wage variable in the data set and estimate the model by fixed effects. How does including these variables affect the coefficients on the criminal justice variables in part (i)
(iii) Do the wage variables in part (ii) all have the expected sign Explain. Are they jointly significant