Stratified sampling / 分层抽样

Stratified sampling: the population is divided into strata according to some variables that are thought to be related to the variables that we are interested in. A sample is taken from each stratum.

分层抽样：根据一些变量将人口分成若干层，这些变量被认为与我们感兴趣的变量有关。从每个层取样。