*
* Example 3.1 from page 75
*
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
*
linreg colgpa
# constant hsgpa act
*
linreg colgpa
# constant act