METHODS an investigation was made by cluster and stratifiedsamplingmethod.
方法采用多阶段分层整群抽样方法入户调查。
2
Stratifiedsamplingmethod was applied to investigate immunization status of ecdemic children and its affecting factors in Baoshan District.
方法采用分层抽样方法对本区外来流动儿童免疫接种现状及其影响因素进行流行病学调查。
3
Stratifiedsamplingmethod, from a polytechnic school in Qingdao test samples were 850, 809 valid questionnaires were valid for the 95.18 percent response rate.