方法采用初级单位含量分层，整群，随机的抽样方法及线索调查。

Methods: Adoppting the elementary units content to divide layer, whole group. Sample method and clue investigation.

youdao

方法采用初级单位含量分层，整群，随机的抽样方法及线索调查。

Methods: Adoppting the elementary units content to divide layer, whole group. Sample method and clue investigation.

youdao