第四章 抽样分布(必威体育精装版)精品.ppt

。 五、不同抽样组织设计的比较 1. 2.类型抽样与整群抽样比较 类型抽样的平均误差与组间方差无关，决定于组内方差的平均水平；整群抽样的平均误差与组内方差无关，决定于组间方差大小。总体方差等于组间方差加上组内方差平均数。我们由此可推导出减小类型抽样与整群抽样平均误差的方法。 (1)减小类型抽样平均误差的办法。提高组间方差，降低组内方差。具体来说，就是使类型抽样的各部分内部单位差异尽可能地小，不同类型间的差异尽可能地大。如果组间方差接近于总体方差，说明组内方差接近于0，这时组内单位基本上没有差异，这是一种极端情况，类型抽样的平均误差接近于0。 (2)减小整群抽样平均误差的办法。为了降低抽样平均误差，应该设法降低群间方差。可通过提高群内方差方法达到降低群间方差目的。因此，类型抽样与整群抽样对总体进行分组的要求刚好是相反的：类型抽样要尽量提高组间方差降低组内方差；整群抽样应尽量提高组内方差降低组间方差。也就是说，类型抽样时，尽量使各组内的单位差异减小，各组间的单位差异增大；整群抽样时刚好相反。 3.阶段抽样平均误差的控制 * 36选7，概率为8347680，平均数为18.5 * 14 * * An estimator is a random variable used to estimate a population parameter (characteristic). Unbiasedness An estimator is unbiased if the mean of its sampling distribution is equal to the population parameter. Efficiency The efficiency of an unbiased estimator is measured by the variance of its sampling distribution. If two estimators, with the same sample size, are both unbiased, then the one with the smaller variance has greater relative efficiency. Consistency An estimator is a consistent estimator of a population parameter if the larger the sample size, the more likely it is that the estimate will come close to the parameter. * An estimator is a random variable used to estimate a population parameter (characteristic). Unbiasedness An estimator is unbiased if the mean of its sampling distribution is equal to the population parameter. Efficiency The efficiency of an unbiased estimator is measured by the variance of its sampling distribution. If two estimators, with the same sample size, are both unbiased, then the one with the smaller variance has greater relative efficiency. Consistency An estimator is a consistent estimator of a population parameter if the larger the sample size, the more likely it is that the estimate will come close to the parameter. * An estimator is a random variable used to estimate a population parameter (characteristic). Unbiasedness An estimator is unbiased if the mean of its sampling distribution is equal to the population parameter. Effi