请教stratified sampling和quota sampling的区别这两个到底有什么区别啊?不要只是翻译

请教stratified sampling和quota sampling的区别这两个到底有什么区别啊?不要只是翻译 stratified teaching是什么意思 翻译“We used a stratified,multistage,cluster-sampling design.” Ei&SCi检索查询：Gas-water Stratified Flow Identification Based on Electromagnetic Image Logging 请教 1) simple random sample 2) stratified sampling 3)systematic random samples 4) cluster sampling 5)multistage samples. 这里them指代谁stratified societies are marked by differences among people that identify them as being higher or lower ei检索查询 A Stratified Image-Hiding Method Based on Chaos 谢谢Digital image watermarking robust to geometric attacks based on Wavelet domainEI检索号：谢谢 Ventura 是什么意思.请教请教 英语翻译IMS HEALTH,Canada,provided an estimate of the total number of antibiotic prescriptions dispensed in Canadian retail pharmacies based on a representative sample of 2000 pharmacies stratified according to type,size,and province.A representa 请教英语试题 请教几道高数题 线性代数；请教, ,请教中文翻译, 请教红印里字 几题奥术请教 请教“不愤不启, 生物请教