Use the data in INJURY.RAW for this exercise.
(i) Using the data for Kentucky, reestimate equation (13.12), adding as explanatory variables male, married, and a full set of industry and injury type dummy variables. How does the estimate on afchnge-highearn change when these other factors are controlled for? Is the estimate still statistically significant?
(ii) What do you make of the small R-squared from part (i)? Does this mean the equation is useless?
(iii) Estimate equation (13.12) using the data for Michigan. Compare the estimates on the interaction term for Michigan and Kentucky. Is the Michigan estimate statistically significant? What do you make of this?