方法对社区人群采用多阶段分层整群随机抽样方法抽取研究对象，进行个案调查和血清学检测。
Methods Subjects were collected from community population by stratified multi-stage cluster sampling method. The data gathered from case investigation and serological detection.
方法采用多阶段分层随机抽样方法，选取了400例正常儿童和25例孤独症儿童为研究对象。
Methods: With the multistage stratified sampling, we randomly selected 400 normal children and 25 autism children as study samples.
方法采用多阶段分层随机抽样方法，选取了400例正常儿童和25例孤独症儿童为研究对象。
Methods: With the multistage stratified sampling, we randomly selected 400 normal children and 25 autism children as study samples.
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