Theorem 8.4 Consider all N! finite populations that are formed by the N permutations of number y Then ,on the average over these finite population,
Note that V is the same for all permutation.
THIS RESULT, proved by W.G. and L.H. Madow (1994), shows that if the order of the items in a specific finite population can be regarded as drawn at random from the N permutation, systematic sampling is on the average equivalent to simple random sampling.
The second approach is to regard the finite populations as drawn at random from an infinite super population which has certain properties. The result that is proved dose not apply to any single finite population (i.e., to any specific set of values y)but to the average of all finite populations that can be drawn from the infinite population.
The symbol ? denotes averages over all finite populations that can be drawn from this super population.