***********************************************************************
* This is a program that illustrates the use of PROC FREQ in SAS for  *
* comparing two diagnostic tests based on data from one sample.       *
***********************************************************************;

proc format;
value testfmt 1='positive' 2='negative';
run;

data comparison;
input test1 test2 count;
format test1 test2 testfmt.;
cards;
1 1 30
1 2 35
2 1 23
2 2 12
run;

proc freq data=comparison;
tables test1*test2/agree;
weight count;
exact McNem;
title "McNemar's Test for Comparing Sensitivities";
run;