Methods: By using questionnaires with multistagestratified random clustersampling method, 726 valid questionnaires of 800 were backed from the university students in 4 universities in Dalian city.
Multistagestratifiedclustersampling method was used for the sampling.
采用多阶段整群分层抽样方法。
3
Methods Cluster, stratified and multistagesampling was taken. 1261 residents over 40 years old were assigned to fill in the questionnaires designed by WHO.