sampling

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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.
Collins Dictionary of Business, 3rd ed. © 2002, 2005 C Pass, B Lowes, A Pendleton, L Chadwick, D O’Reilly and M Afferson
References in periodicals archive ?
WTD pellet groups were more abundant than moose pellet groups in all sampling units. Twenty-two of the 32 total sampling units (68.8%) contained no moose pellet groups.
Clusters are often called primary sampling units. If all items in the selected clusters are included in the sample, we have single-stage sampling.
It takes a data set from survey sampling, performs a cluster analysis of sampling units, and then examines the stability of the partition at a given level by simulated resampling of the same universe.
However, an increase in the number of selected sampling units entails an increase in the total cost of the CPI.
Data was analyzed using a hierarchial ANOVA model in which teachers were nested within sampling units and sampling units were nested within conditions; teachers and sampling units were treated as random effects while treatment condition was treated as a fixed effect.
Similar to a correlation-type analysis, SADIE results reflect the spatial arrangement of the insects at the sampling unit level (tree) and above, but depend on the pre-existing level of heterogeneity in the data set.
If you wanted to give him the benefit of the doubt, however, you might say that his refusal to allow Tanterari to be dope tested in the sampling unit at Haydock last Thursday was prompted by a genuine concern over the possible spread of infection between sick stables and fit ones, rather than just a convenient excuse to offer two of his most expressive fingers to the body who recently hauled him over the coals with regards to the controversial performances of Celtic Son.
For the kind of community sampling schemes we considered primarily, an observer recorded presence or absence of each species of interest in each of a number of sampling units within a sampling session.
The advantages and efficacy of collecting such data in a CATI environment will allow a portion of all commodities and services to be updated, or rotated, in each sampling unit every year (category rotation), instead of rotating all commodities and services in 20 percent of the sampling units each year (area rotation).
Pipe yesterday claimed support from a number of his fellow trainers after refusing to let Tanterari be routine tested following his run at Haydock on Thursday on the grounds that the sampling unit could be a cause for the spread of infections.
The remaining primary sampling units were assigned to three city-size classes--medium-sized cities, small-sized cities, and nonmetropolitan areas--within the Northeast, North Central, South, and West regions.16 The result of the sampling process was the selection of 39 new areas with the retention of 52 primary sampling units from the old sample, of which 30 were certainty selections in the new sample.