Effect of unequal catchability on estimates of the number of classes in a population
研究证明，当各类别的捕获概率不相等时，两个常用的总体类别数估计量会随机减小，导致负偏差，仅在概率相等时无偏，并给出数值计算展示偏差大小。
It is shown that two well-known estimators of the number of classes in a population decrease stochastically as the capture probabilities of the classes become more unequal (heteroge- neous), in the sense of majorization. Then it follows that the estimators are unbiased only when the capture probabilities are equal, otherwise they are negatively biased. Some numerical calculations are presented to exhibit the magnitude of the biases.