*
* Example 7.2 from page 223
*
open data gpa1.raw
data(format=free,org=columns) 1 141 age soph junior senior senior5 male campus business $
  engineer colgpa hsgpa act job19 job20 drive bike walk voluntr pc greek car siblings $
  bgfriend clubs skipped alcohol gradmi fathcoll mothcoll
*
* With controls
*
linreg colgpa
# constant pc hsgpa act
*
* Without control
*
linreg colgpa
# constant pc