Horwitz-Thompson (HT) estimator

An algorithm for estimating the population totals (e.g., total number of fish) in a population based on a sample, and for estimating its variance. (interpreted from Lohr, p. 196-197) A method of estimating the population total when sampling without replacement from a finite population and when unequal probabilities of selection are used. The estimator is unbiased, linear and can be used with a variety of basic sample designs (ISI; Horvitz and Thompson, 1952).