On the inclusion probabilities in some unequal probability sampling plans without replacement

Comparison results are obtained for the inclusion probabilities in some unequal probability sampling plans without replacement. For either successive sampling or Hájek’s rejective sampling, the larger the sample size, the more uniform the inclusion probabilities in the sense of majorization. In particular, the inclusion probabilities are more uniform than the drawing probabilities. For the same sample size, and given the same set of drawing probabilities, the inclusion probabilities are more uniform for rejective sampling than for successive sampling. This last result confirms a conjecture of Hájek (Sampling from a Finite Population (1981) Dekker). Results are also presented in terms of the Kullback–Leibler divergence, showing that the inclusion probabilities for successive sampling are more proportional to the drawing probabilities.