In reply to Ksharp.

Yes, PROC OPTEX can assign units to treatment groups so that certain moments (mean, standard deviation, skewness,...) are as close as possible between groups. If the number of units is divisible by the number of groups, then this is a solution to the partition problem. However, the SUM and the MEAN are not equivalent when the group sizes are different. For example, the last example in this article has 11 items and 2 groups. One solution is G1 = {1.6, 1.8, 1.9, 2, 2.2} and G2 = {0.8, 1.2, 1.3, 1.4, 2.3, 2.5}. Although the sums are equal, the means are not. So the PROC OPTEX method does not solve the partition problem for this example.