Estimation in sampling on two successive occasions

For estimating the mean of a finite population on the second of two successive occasions from a simple random sample, the authors [1] have proposedelsewhere an estimate which utilizes the data obtained from the sample on the first occasion as ancillary information. In this paper, it is shown that this estimate is more efficient than the one similar to that of Pathak and Rao [2] in all situations where the well known ratio estimate in simple random sampling is no less efficient than the usual regression estimate or the Rao-Hartley-Cochran estimate in sampling with varying probabilities and without replacement.