********************************************************************************;
*
*       Hypothesis Testing and the Quadratic Regression Model
*
********************************************************************************;
# delimit ;
clear;
cap log close;

********************************************************************************;
*
*       Specify the output file
*
********************************************************************************;
log using Quad.log,replace;
set more off;

********************************************************************************;
*
*       Read in and summarize the data
*
********************************************************************************;
use     caschool.dta;
describe;
summarize testscr avginc;

********************************************************************************;
*
*       Form quadratic income term
*
********************************************************************************;
gen     inc2 = avginc^2;

********************************************************************************;
*
*       Estimate the quadratic model
*
********************************************************************************;
reg     testscr avginc inc2 ,r;
test    inc2;
test    avginc + 21*inc2=0;
test    avginc + 81*inc2=0;
scalar  Poor10 = _b[_cons] + 10*_b[avginc] + (10^2)*_b[inc2];
scalar  Poor11 = _b[_cons] + 11*_b[avginc] + (11^2)*_b[inc2];
scalar  Rich40 = _b[_cons] + 40*_b[avginc] + (40^2)*_b[inc2];
scalar  Rich41 = _b[_cons] + 41*_b[avginc] + (41^2)*_b[inc2];
scalar  DeltaP = _b[avginc] + (21)*_b[inc2];
scalar  DelraR = _b[avginc] + (81)*_b[inc2];
scalar  list;

log close;
*clear;
*exit;