# sampling

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Related to two-stage sampling: Cluster sampling

## sampling

the selection of part of a total population of consumers or products whose behaviour or performance can be analysed, in order to make inferences about the behaviour or performance of the total population, without the difficulty and expense of undertaking a complete census of the whole population.

Samples may be chosen randomly, with every consumer or product in the population having an equal chance of being included. Random samples are most commonly used by firms in QUALITY CONTROL where they are used as a basis for selecting products, components or materials for quality testing.

Alternatively, samples may be chosen by dividing up the total population into a number of distinct sub-groups or strata, then selecting a proportionate number of consumers or products from each sub-group since this is quicker and cheaper than random sampling. In MARKETING RESEARCH and opinion polling, quota sampling is usually employed where interviewers select the particular consumers to be interviewed, choosing the numbers of these consumers in proportion to their occurrence in the total population.

Samples may be:

1. cross-sectional, where sample observations are collected at a particular point in time, for example data on company sales and the incomes of consumers in the current year, embracing a wide range of different income groups, as a basis for investigating the relationship between sales and income;
2. longitudinal, where sample observations are collected over a number of time periods, for example data on changes in company sales over a number of years and changes in consumer incomes over the same time periods, as a basis for investigating the relationship between sales and income. See STATISTICAL INFERENCES, QUESTIONNAIRE.
References in periodicals archive ?
To examine the effect of variation between elements in the two-stage sampling design, sampling four quadrats per station, we created a simple formula in Excel (Microsoft, Seattle, WA) that randomly selected one of the four quadrats from each station and then calculated the means and variances for each survey area.
However, a two-stage sampling design could be considered in which beach segments are selected at the 1st stage and sediment cores within segments are selected at the 2nd stage.
Side-by-side comparisons with the six-stage version, however, revealed an approximately 40 percent lower recovery rate of bacteria with the two-stage sampling device, except when the device was sampling dilute concentrations of particles larger than 1 [micro]m.
If we take a random subsample of the items in the cluster, we have two-stage sampling.
The research reported in this volume illustrates the kinds of research questions about work and organizations that can and cannot be addressed adequately with a general-purpose survey questionnaire administered via a cross-sectional, two-stage sampling of employees and informants from the establishments that employ them.

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