方法采用整群抽样的方法，对1200名军事飞行人员进行问卷调查。
Methods a questionnaire survey of occurrence of SAHS in terms of random sampling was performed in 1200 military pilots.
方法采用整群抽样的方法在合肥市某中专学校进行问卷调查，并对有效问卷进行统计分析。
Methods Using cluster sampling, the study was conducted in a secondary technical school in Hefei, and the available questionnaire were analysed.
方法采用整群抽样的方法在合肥市某中专学校进行问卷调查，并对有效问卷进行统计分析。
Methods using cluster sampling , the study was conducted in a secondary technical school in hefei , and the available questionnaire were analysed.
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