Large-scale sample surveys are always undertaken with stratified multi-stage sampling.
大型抽样调查总是采用分层多阶段抽样。
Methods the study sample was got by multi-stage randomized sampling, and the injury information of the inhabitants aged over 18 years in Guangdong province was collected by questionnaire.
方法按分层整群抽样的方法抽取样本，并通过问卷调查的方式收集有关广东省18岁以上居民的伤害信息。
A multi-station rotary sample stage is disclosed.
一种多工位旋转样品台。
We give the approximation formulas of the variance of the sample ratio estimator for a population mean and its asymptotically non-biased estimator in multi-stage sampling.
讨论多阶段抽样比率估计及其样本量选择的问题，给出了比率估计抽样均方误差的近似公式及其渐近无偏估计的公式。
We give the approximation formulas of the variance of the sample ratio estimator for a population mean and its asymptotically non-biased estimator in multi-stage sampling.
讨论多阶段抽样比率估计及其样本量选择的问题，给出了比率估计抽样均方误差的近似公式及其渐近无偏估计的公式。
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