Weed survey was conducted by sampling methods of inverted W-pattern to determine the species composition and structure of weed communities in maize fields in Hebei Province.
采用倒置“W”取样法对河北省玉米田杂草进行了调查，以明确田间杂草的种类组成及群落结构。
Methods a questionnaire survey was conducted among 200 people in Luohu District, selected by random sampling.
方法在社区采用单纯随机抽样的方法抽取居民200人进行问卷调查。
Methods An anonymous survey was conducted among 502 students from a technical college selected by stratified sampling and cluster sampling.
方法采用分层整群抽样的方法对一所职业技术学院的502名学生进行匿名式问卷调查。
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