stratified sample

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Related to stratified samples: Stratified random sampling

stratified sample

a SAMPLE which is selected by first stratifying the parent population. The procedure involves dividing the population into strata relevant to the study to be undertaken, e.g. for a study of voting intention, social class and age may be relevant; for a study of attitudes to the benefit system, income level and employment status would be relevant. When the strata have been identified RANDOM SAMPLES are taken from each. As long as these samples are of sizes proportionate to the size of each stratum within the parent population (proportionate stratification), this method allows improved precision, particularly if a sample is being taken from a relatively large population, since it introduces some controlled restrictions on selection. However, disproportionate stratification may be used if a stratum is too small to yield a sufficiently large sample for analysis if the criterion for selection used in other strata is adopted.
Collins Dictionary of Sociology, 3rd ed. © HarperCollins Publishers 2000
References in periodicals archive ?
In order to obtain a biased stratified sample, we simulated a two-phase random selection process from the population (Figure 1(a)) such that P(Y = 1 | S) = 0.5 and P([X.sub.e] = 1 | S) = 0.5.
Table 1 helps to explain the different behaviors of the two classifiers: Correction approaches are based on one or several of the principles (i) IP weighting, (ii) rebuilding the original covariance structure, and (iii) increasing the number of learning observations as compared to the stratified sample. Obviously, weighting (Property (i)) should be applied in order to obtain any improvement in performance.
Due to these issues, sample size in terms of number of clusters and items selected from each cluster should be greater than the sample size required for a simple random sample or stratified sample.
The first term of the variance equation is the variance of a stratified sample mean under proportional allocation.