Pollock K H, Lancia R A, Conner M C, Wood B L
Biometrics. 1985 Sep;41(3):653-62.
The change-in-ratio technique is a useful practical procedure for the estimation of game animal population sizes. The major problem with this technique is failure of the assumption that both types of animals are captured or sighted with equal probabilities. Here we extend the change-in-ratio technique to the case where there are two removals with emphasis on the special situation where there are two consecutive single-type removals. The advantage of this extension is that it allows an estimation procedure which is robust to unequal capture or sighting probabilities. It is also possible to test the assumption of equal sighting probabilities. Some numerical results on mean squared error of the population size estimator for the new design and the traditional design are given. The procedure is illustrated on some juvenile grass carp data collected in a small pond where the population size is known. We believe this technique is potentially useful to wildlife and fisheries biologists and that more statistical research would be beneficial.
比率变化技术是一种用于估计猎物种群数量的实用方法。该技术的主要问题在于，其假设两种类型的动物被捕获或被观察到的概率相等，但这一假设并不成立。在此，我们将比率变化技术扩展到有两次移除情况的案例中，重点关注连续两次单一类型移除的特殊情况。这种扩展的优势在于，它允许采用一种对不等的捕获或观察概率具有稳健性的估计程序。同时，也能够检验观察概率相等这一假设。文中给出了新设计和传统设计的种群数量估计器的均方误差的一些数值结果。该程序通过在一个已知种群数量的小池塘中收集的一些幼草鱼数据进行了说明。我们认为，这项技术对野生动物和渔业生物学家可能具有潜在用途，并且更多的统计研究将是有益的。
