par Berger, Yves
Référence Journal of statistical planning and inference, 74, 1, page (149-168)
Publication Publié, 1998-10
Article révisé par les pairs
Résumé : Drawing distinct units without replacement and with unequal probabilities from a population is a problem often considered in the literature (e.g. , Int. Statist. Rev. 48, 317-355). In such a case, the sample mean is a biased estimator of the population mean. For this reason, we use the unbiased Horvitz-Thompson estimator (1951). In this work, we focus our interest on the variance of this estimator. The variance is cumbersome to compute because it requires the calculation of a large number of second-order inclusion probabilities. It would be helpful to use an approximation that does not need heavy calculations. The variance approximation provides this advantage as it is free of second-order inclusion probabilities. proved that this approximation is valid under restrictive conditions that are usually not fulfilled in practice. In this paper, we give more general conditions and we show that this approximation remains acceptable for most practical problems.