StratifiedSampling

:ClusterSampling -- MultistageSampling -- SimpleRandomSampling

When subpopulations of the population to be studied vary considerably, it is advantageous to sample each subpopulation (stratum) independently and produce a WeightedMean that has less variability than the MeaN of a random sample. There are several possible strategies:

Proportionate allocation uses the same SamplingFraction in each of the strata.

Optimum allocation takes larger samples in the strata with the greatest variability to generate the least possible sampling variance.

DickBeldin