*
* Example 7.11 from page 236
*
open data mlb1.raw
data(format=free,org=columns) 1 353 salary teamsal nl years games atbats runs hits doubles triples hruns rbis bavg bb so sbases fldperc frstbase scndbase shrtstop thrdbase outfield catcher $
  yrsallst hispan black whitepop blackpop hisppop pcinc gamesyr hrunsyr atbatsyr allstar slugavg rbisyr sbasesyr runsyr percwhte $
  percblck perchisp blckpb hispph whtepw blckph hisppb lsalary
*
linreg lsalary
# constant years gamesyr bavg hrunsyr rbisyr runsyr fldperc allstar black hispan blckpb hispph
*
* Joint test of the four race variables
*
exclude
# black hispan blckpb hispph