方法采用整群抽样与典型调查结合的方法进行现场调查，结合临床检查、生化分析和毒理学方法进行实验室检测。
Methods Using cluster sampling and typical investigation, a spot research was taken while experimental indexes were determined by clinical, biochemical and toxicologic methods.
方法采取现场无记名自主填写调查表，对应用二阶段抽样法随机抽取的1800名社区居民进行调查。
Methods The questionnaire survey forms were filled out on-the spot by 1800 residents who were at random selected.
大规模现场调查，由于情况复杂、影响因素多，往往采用多阶段混合型随机抽样方法。
In large scale field surveys, multistage sampling is applied because the situations are complex and there are many influencing factors.
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