* Reference: Chapters 4 and 7 of
* Jeffrey M. Wooldridge, Introductory Econometrics: A Modern Approach,
* South-Western College Publishing, 2000.
SAMPLE 1 353
READ (MLB1.shd) 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 

SET MISSVALU=-999
SET SKIPMISS
SET NOWARNMISS

* Section 4.5
* Equation (4.31), p. 140.
OLS lsalary years gamesyr bavg hrunsyr rbisyr
* Test the hypothesis that the variables bavg, hrunsyr and rbisyr
* have no effect on players' salaries. 
* See the F statistic on p. 145.
* The TEST command is used for calculating F-test statistics
* for testing a joint hypothesis.
TEST
 TEST bavg=0 
 TEST hrunsyr=0  
 TEST rbisyr=0
END

* Example 7.11
* Generate interaction variables
GENR blckpb=black*percblck
GENR hispph=hispan*perchisp
* Obtain summary statistics on the percentages of blacks and
* Hispanics in the cities in the sample.
STAT percblck perchisp
* Equation (7.19), p. 229
OLS lsalary years gamesyr bavg hrunsyr rbisyr runsyr fldperc &
            allstar black hispan blckpb hispph
* Test of significance
TEST 
 TEST black=0
 TEST hispan=0
 TEST blckpb=0
 TEST hispph=0
END
* In a city with 10% blacks, estimate the impact on salary for blacks 
* compared to whites.
TEST black+blckpb*10
* In a city with 20% blacks, estimate the impact on salary for blacks 
* compared to whites.
TEST black+blckpb*20
* Find the percentage of Hispanics required to make a zero differential
* between whites and Hispanics.
TEST -hispan/hispph
STOP