Methods Random sampling investigation was carried out by self-administering and anonymous questionnaire among college students in Henan.
方法采用不记名自填问卷方式，对河南在校大学生进行随机抽样调查。
Methods General investigation was adopted to understand the water supply situation in rural areas and stratified random sampling was used to monitor the water quality.
方法按照相关调查表要求，对农村供水情况进行普查，供水水质采用分层随机抽样的方法进行监测。
DESIGN: a stratified random cluster sampling investigation.
设计：分层整群抽样调查。
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