*******************************************************************************
* This program in SAS provides a permuted blocks randomization scheme for     *
* equal allocation of two treatments, denoted as A and B.                     *
*                                                                             *
* The user needs to specify values for the desired sample size (sampsize)     *
* and the desired block size (blcksize).                                      *
*******************************************************************************;

data values;
samplesize=48;
blocksize=6;
run;

data random;
set values;
nblocks=round(samplesize/blocksize);
na=round(blocksize/2);
nb=blocksize-na;
do block=1 to nblocks by 1;
   nna=0;
   nnb=0;
   do i=1 to blocksize;
      subject=i+((block-1)*blocksize);
      if nna=na then treatment="B";
      if nnb=nb then treatment="A";
      else do;
         aprob=(na-nna)/(na+nb-nna-nnb);
         u=ranuni(0);
         if (0<=u<=aprob) then do;
            treatment="A";
            nna=nna+1;
         end;
         if (aprob<u<=1) then do;
            treatment="B";
            nnb=nnb+1;
         end;
      end;
      keep subject treatment;
      output;
   end;
end;
run;

proc print data=random;
id subject;
var treatment;
title "Randomization Plan for Equal Allocation of Treatments A and B";
run;