# PS5.5, for the second application in Section 5.4 
open data4-6
corr urb famsize unemp highschl college medinc
# Model A -- most general specification 
ols povrate const urb famsize unemp highschl college medinc
# Model B -- omit unemp with the highest p-value 
omit unemp
# Model C after omitting urb 
omit urb
# Model D -- exclude medinc 
omit medinc
# Relate medinc to its determinants and confirm multicollinearity 
ols medinc 0 famsize unemp highschl college