网站首页 英语词典
Methods A large - scale survey was conducted at 250 medical health units based on stratified sampling.
方法使用分层抽样的方法在全国范围内抽取250家医疗机构开展大规模调查.
互联网
Methods: With stratified sampling and cluster sampling, we investigate 487 families in poverty.
方法采用分层整群抽样方法调查487户贫困家庭.
分层抽样???
国先网英语在线翻译词典收录了4367410条英语词汇在线翻译词条，基本涵盖了全部常用英语词汇的中英文双语翻译及用法，是英语学习的有利工具。