# PS4.4, for Table 4.4 and the application in Section 4.6 
open data4-4
ols BUSTRAVL 0 FARE GASPRICE INCOME POP DENSITY LANDAREA
# omit variables -- Model B  
omit GASPRICE LANDAREA FARE 
# estimate full model and omit variables one at a time 
ols BUSTRAVL 0 FARE GASPRICE INCOME POP DENSITY LANDAREA 
# Model C 
omit GASPRICE
# Model D 
omit LANDAREA
