options nodate pagesize=54 linesize=80;

/* Read in the input file   */

data ex0504;
* infile '../../../data/biostat/ex0504.dat';
infile 'C:\biostat\data\ex0504.dat';
input trt improve trt_r imp_r;
run;

/* Obtain crosstabs and risk difference based on reversed trt and improve (SAS default is to model
the probability in the "lowest" category) */

proc freq;
table trt_r*imp_r / riskdiff;
run;

quit;