Stratified Sampling

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Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In statistics, stratified sampling is a method of sampling from a population. When sub-populations vary considerably, it is advantageous to sample each subpopulation independently. Stratification is the process of grouping members of the population into relatively homogeneous subgroups before sampling. The strata should be mutually exclusive: every element in the population must be assigned to only one stratum. The strata should also be collectively exhaustive: no population element can be excluded. Then random or systematic sampling is applied within each stratum. This often improves the representativeness of the sample by reducing sampling error. It can produce a weighted mean that has less variability than the arithmetic mean of a simple random sample of the population.

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Pagina's: 76, Paperback, Betascript Publishers