方法采用多级随机抽样法。

Methods Stratified random group sampling was adopted in survey.

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方法：(1)抽样方法：采用多级随机抽样法。

Methods: (1) sampling method: Apply multilevel and random sampling method.

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方法：(1)抽样方法：采用多级随机抽样法。

Methods: (1) sampling method: Apply multilevel and random sampling method.

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