Introduction to Power and Sample Size Analysis

If you want to perform a power computation for an analysis that is not currently supported directly in SAS/STAT tools, and you have a power formula, then you can program the formula in the DATA step.

For purposes of illustration, here is the power formula in the section Computing Power and Sample Size implemented in the DATA step to compute power for the t test example:

data tpow;
   do meandiff = 5, 6;
      do stddev = 12, 18;
         do alpha = 0.05, 0.1;
            do ntotal = 100, 200;
               ncp = ntotal * 0.5 * 0.5 * meandiff**2 / stddev**2;
               critval = finv(1-alpha, 1, ntotal-2, 0);
               power = sdf('f', critval, 1, ntotal-2, ncp);
               output;
            end;
         end;
      end;
   end;
run;

proc print data=tpow;
run;

The output is shown in Figure 18.6.