/* InferenceForTheDifferenceOfTwoProportions.sas */
/* Inference for the difference of two proportions */
/* Confidence intervals and tests for the ratio of two proportions */
/* ---------------------------------------------------------*/
/* examples from chapter 6 */
/* ---------------------------------------------------------*/
/* ---------------------------------------------------------*/
/* LeadingQuestion.sas */
/* leading question regarding gun permits example */
data permit;
   input group $ response $ count;
   label response='favor permit';
cards;
leadingQ favor  403
leadingQ not    182
neutralQ favor  463
neutralQ not    152
;
proc freq data=permit order=data;
   tables group*response / alpha=.05 nocol nopercent riskdiff (cl=wald equal);
   weight count;
   ods select CrossTabFreqs RiskDiffCol1 PdiffTest; 
title 'leading question regarding gun permits example (success = favor permit)';
/* ------------------------------------------------------ */
/* HIV-VaccineTrial.sas */
/* HIV vaccine trial */
data hiv;
   input group $ response $ count;
   label response='HIV status';
cards;
vaccine positive  241
vaccine negative 3357
control positive  126
control negative 1679
;
proc freq data=hiv order=data;
   tables group*response /  alpha=.05 nocol nopercent riskdiff (cl=wald equal);
   weight count;
   ods select CrossTabFreqs RiskDiffCol1 PdiffTest;
title 'HIV vaccine trial (success = positive)';
/* ------------------------------------------------------ */
/* ScotlandCoronaryStudy.sas */
/* West of Scotland coronary prevention study */
/* Initial 5 year study period */
data scotland1;
   input drug : $ 11. response $ count;
   label response='has a coronary event';
cards;
pravastatin yes  174
pravastatin no  3128
placebo     yes  248
placebo     no  3045
;
proc freq data=scotland1 order=data;
   tables drug*response / alpha=.05 nocol nopercent riskdiff (cl=wald equal);
   weight count;
   ods select CrossTabFreqs RiskDiffCol1 PdiffTest;
title 'West of Scotland coronary prevention study: 5 years (success=yes)';
/* ------------------------------------------------------ */
/* 5 years plus 10 year followup study */
data scotland2;
   input drug : $ 11. response $ count;
   label response='has a coronary event';
cards;
pravastatin yes  390
pravastatin no  2912
placebo     yes  509
placebo     no  2784
;
proc freq data=scotland2 order=data;
   tables drug*response / alpha=.05 nocol nopercent riskdif (cl=wald equal);
   weight count;
   ods select CrossTabFreqs RiskDiffCol1 PdiffTest; 
title 'West of Scotland coronary prevention study: 15 years (success=yes)';
/* ------------------------------------------------------ */
run;