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。
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。
Methods. The survey was conducted according to multi-stage stratified cluster sampling method.
方法：分阶段分层整群随机抽样调查。
Methods A total of 7482 residents aged 15-69 selected in representative 30 counties through multi-stage random sampling from Zhejiang Province were surveyed by using questionnaire.
方法采用多阶段随机抽样的方法，在浙江省有代表性的30个县区，对7482名年龄在15～69岁的居民进行面对面问卷调查。
Methods Subjects were collected from community population by stratified multi-stage cluster sampling method. The data gathered from case investigation and serological detection.
方法对社区人群采用多阶段分层整群随机抽样方法抽取研究对象，进行个案调查和血清学检测。
RESEARCH METHODThe stratified multi-stage cluster random sampling method was used in the survey.
研究方法本研究采用分层整群随机抽样方法进行抽样。
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。
Methods 1356 employees of 7 enterprises from 7 districts of Shenzhen City were selected by multi-stage random sampling and investigated by questionnaires.
方法采用多层随机抽样方法，抽取深圳市7个区7家企业1356名员工进行健康素养现状调查。
Method A multi-stage stratified cluster sampling survey on health condition of 14486 residents was taken in 2007.
方法：采用多阶段分层整群抽样方法，对2007年居民家庭健康状况入户调查，共调查14 486人。
Method A multi-stage stratified cluster sampling survey on health condition of 14486 residents was taken in 2007.
方法：采用多阶段分层整群抽样方法，对2007年居民家庭健康状况入户调查，共调查14 486人。
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