options formdlim = '-';

data vitc;
  input trt $ cold $ n;     
cards;
Placebo Yes 335
Placebo No   76
Vit.C   Yes 302
Vit.C   No  105
;

proc freq;
  table trt*cold / norow nocol nopercent chisq measures cl;
  weight n;
  title 'Chi-square test';
  
/* Here's how to do a chi-square test when each observation is one case */
/*  this is made up data */
/*  A has 2 levels, B has 3 */

data madeup;
  input a b;
cards;
1 1
0 1
1 2
1 1
0 1 
0 2
0 2
0 1
1 0
1 0
0 0 
0 0 
0 0
;
proc freq;
  table a*b /norow nocol nopercent chisq ;
  title 'Chi-square test, starting with individual obs.';
run;