/*
 *
 *  This is the SAS file for Homework #2 for
 *  90-771 for Spring, 2005
 *
 *
 */


options linesize=80;
options pagesize=60;


filename mepsraw 'MEPSextract1996.txt';
data MEPS;
  infile mepsraw;
  input age sex income employed insured health spending;

proc contents;
proc means;
proc corr;
proc freq;
  table insured;
  table insured*employed;

data MEPS;
  set MEPS;
  incomeK = income/1000;
  drop income;

proc means;

proc reg;
  model insured = age sex employed incomeK / ACOV;
  output out=ols_pred pred=Yhat;
  title "Linear probability model";

data ols_pred;
  set ols_pred;
  label Yhat=' ';
  Yhat01 = (Yhat>1 OR Yhat<0);

proc means data=ols_pred;
  title "LPM predicted probabilities";

proc logistic descending data=MEPS;
  model insured = age sex employed incomeK;
  output out=logit_out prob=Phat Xbeta=Ystarhat;
  title "Logit model";

data logit_out;
  set logit_out;
  label Ystarhat=' ';
  label Phat=' ';
  drop _LEVEL_;

proc logistic descending data=MEPS;
  model insured = age sex employed incomeK / link=probit;
  output out=probit_out prob=Phat Xbeta=Ystarhat;
  title "Probit model";

data probit_out;
  set probit_out;
  label Ystarhat=' ';
  label Phat=' ';
  drop _LEVEL_;

data logit_out;
  set logit_out;

  me_incK = Phat*(1-Phat)*(0.0451);

proc means;
  var Phat me_incK;
  title "Logit marginal effects";


data probit_out;
  set probit_out;

  me_incK = pdf('NORMAL',Ystarhat,0,1)*(0.0204);

proc means;
  var Phat me_incK;
  title "Probit marginal effects";

proc logistic descending data=MEPS;
  model insured = employed incomeK / link=probit;
  output out=logit_out prob=Phat Xbeta=Ystarhat;
  title "Probit model --- testing joint hypothesis";