# PS4.3 for Examples 4.12 and 4.13 in Section 4.5 
open data4-3
ols housing 0 gnp intrate 
# Model B in Example 4.12 
omit intrate
# Model C in Example 4.13 
ols housing 0 gnp intrate pop unemp
# Wald test for omitting pop and unemp 
omit pop unemp 
# add unemp back for Practice Problem 4.8 
add unemp