1、Methods With stratified sampling and cluster sampling, we investigate 487 families in poverty.
方法采用分層整群抽樣方法調查487戶貧困家庭。

2、Stratified sampling can reduce the sampling error associated with simple random samples.
分層抽樣可以減少由簡單隨機抽樣造成的抽樣誤差。

3、Methods: The stratified sampling and cluster random sampling methods are used in this survey.
方法：本研究采用分層隨機抽樣方法和整群隨機抽樣方法。

stratified sampling翻譯