stratified sample


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Related to stratified sample: Simple random sample, Systematic sample

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.
References in periodicals archive ?
First, a factorial ANOVA (Heppner, Wampold, & Kivlighan, 2008) was conducted to evaluate the percentage of students passing ELA and Math assessments within all RAMP schools (2007, 2008, and 2009) compared to a stratified sample of students attending control schools using one data point in time only (2009 percent passing rates).
Stratified samples ensure that the sample proportion for the stratifying characteristic is identical to the population proportion, reducing sampling error and improving the accuracy of inferences.
A stratified sample was drawn from the publication's rankings based upon the multiple national and regional categories of the undergraduate school rankings.
If the variance of the observed characteristic within each stratum is smaller than that for the entire population, as is usually true, the reliability of the sample for a given size will be better or the efficiency for a given degree of reliability will be greater because we used a stratified sample.
For example, a four-cavity machine could be producing four distinctly different populations (strata) and the choice of selecting a random or stratified sample affects the sensitivity of detecting a shift in one or more strata.
Although there was no statistically significant difference in the indicators of fertility between linked and unlinked cases, the differential in linkage rates was considerably more pronounced in its biasing effect than the modest departures of the 1910 stratified sample from the national public use sample of that year.
An independent research firm will select a stratified sample of senior credit, finance and sales/marketing professionals to participate in the focus groups.
The stratified sample includes 270 children which is not a small sample considering the resource and time expended on individually administered devices specially with very young children.
The information about daily newspapers is derived from a changed model adopted by the Newspaper Association of America that uses a stratified sample of U.
Although it is hard to draw population conclusions from a stratified sample of this type, two impressions struck me.
The purpose of this study was to determine if there were significant similarities or differences in problem-solving orientations and decision-making styles among a stratified sample of rehabilitation practitioners.