Modified construction of random groups in Rao, Hartley and Cochran’s scheme: To increase its practical applicability

In their modified method of random groups construction in the Rao, Hartley and Cochran's (RHC) scheme, Singh and Lal (1978) use Midzuno's scheme of sampling for construction of first random group while the remaining (n-1) random groups are constructed as usual. For the general case of unequal random group sizes, Singh and Lal have given a condition under which their strategy fares better than the usual RHC strategy. The strategy proposed in this paper has been shown to be complementary that of Singh and Lal in the sense that whenever Singh and Lal‘s strategy is less efficient than the usual RHC strategy, the proposed strategy is more efficient than the RHC strategy and vice-versa. In case of equal random group sizes, all the three strategies have been shown to be equally efficient.