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Chapter 7

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Chapter 7

The Logic Of SamplingKey Terms

- Nonprobability samplingTechnique in which samples are selected in a way that is not suggested by probability theory.

- Purposive (judgmental) samplingSelecting a sample based on the knowledge of a population, it's elements and the purpose of the study.

- Snowball samplingResearcher collects data on members of the target population that can be located, then asks those individuals to provide the information to locate other members.

- Quota samplingUnits are selected into a sample on the basis of prespecified characteristics, so the total sample will have the same distribution of characteristics assumed to exist in the population being studied.

- Probability samplingSamples are selected in accord with probability theory, typically involving some random selection mechanism.

- RepresentativenessQuality of a sample having the same distribution of characteristics as the population from which it was selected.

- EPSEMEqual probability of selection method.
- ElementUnit about which information is collected and that provides the basis of analysis.

- PopulationThe theoretically specified aggregation of study elements.
- Study populationAggregation of elements from which the sample is actually selected.

- Random selectionEach element has an equal chance of selection independent of any other event in the selection process.
- Sampling unitElement or set of elements considered for selection in some stage of sampling.

- ParameterSummary description of a given variable in a population.
- StatisticSummary description of a variable in a sample.

- Sampling errorThe degree of error to be expected of a given sample design.
- Confidence levelExpression of the accuracy of sample statistics.

- Confidence intervalRange of values within which a population parameter is estimated to lie.
- Sampling frameList or quasi list of elements from which a probability sample is selected.

- Simple random samplingBasic sampling method assumed in the statistical computations of social research.
- Systematic samplingEvery kth element in the total list is chosen for inclusion in the sample.

- Sampling intervalStandard distance between elements selected in the sample.
- Sampling ratioProportion of elements in the population that are selected.

- StratificationGrouping of units composing a population into homogenous groups before sampling.

- Cluster samplingA multistage sampling in which natural groups are sampled initially with the members of each selected group being subsampled afterward.

- PPSProbability proportionate to size.
- WeightingGiving some cases more weight than others.