Hygiene investigation was carried out in 156 classrooms of 36 schools with stratificationsampling.
采用分层抽样方法，对36所学校、156间教室进行卫生学调查。
2
Stratification is one of the key techniques in stratified sampling investigation and monitoring using remotely sensed data.
分层技术是遥感分层抽样调查与监测方法中的关键技术之一。
3
Methods the sampled students, which were taken out from the all middle schools in Sanming city by means of randomized stratification cluster sampling, were investigated with AAT (adaptability test).