* PS6.7 using DATA6-4 for Example 6.5 
SAMPLE 1 49
READ(data6-4) WAGE EDUC EXPER AGE
GENR LNWAGE=LOG(WAGE)
GENR EDUC2=EDUC**2
GENR EXPER2=EXPER**2
GENR AGE2=AGE**2
*
* Estimate the model to determine if education, experience and age have
* a quadratic effect.  The LOGLIN option is specified on the OLS command
* since the dependent variable, WAGE, is in logged form and the independent
* variables, EDUC, EXPER, AGE, EDUC2 EXPER2, and AGE2 are in linear form.
* If the LOGLIN option is NOT specified then the ELASTICITY AT MEANS in
* OLS regression output will be incorrect.
*
OLS LNWAGE EDUC EXPER AGE EDUC2 EXPER2 AGE2 / LOGLIN
* omit variables one at a time
OLS LNWAGE EDUC EXPER EDUC2 EXPER2 AGE2 / LOGLIN
OLS LNWAGE EDUC EXPER EDUC2 EXPER2 / LOGLIN
OLS LNWAGE EDUC EXPER EDUC2 / LOGLIN
OLS LNWAGE EDUC2 EXPER / LOGLIN 
*
DELETE / ALL
STOP