Stratified sampling (STR)

In stratified sampling, the target population is divided into non-overlapping subpopulations called strata. These are conceptually regarded as separate populations in which sampling can be performed independently. To carry out stratification, appropriate auxiliary information is required in the sampling frame. Regional, demographic and sosioeconomic variables are often used as the stratifying auxiliary variables. See pages 16 and 61 in Lehtonen, R & Pahkinen, E. (2004)

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