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.
References in periodicals archive ?
Systematic Sampling. The systematic sampling design is based on the number of samples, and fixed intervals were used to obtain sample blocks.
The estimator typically considered is based on circular systematic sampling and takes the form
- systematic sampling of all quartz vein exposures defined from the above;
The statements such as selection of cases is typically done by purposive sampling in case-control studies; estimates based on sample surveys are more accurate than those based on total enumeration; the only advantage of systematic sampling over random sampling technique is its simplicity; population is a group of individuals in the population are some such examples.
The prescribed number of beneficiaries house holds were selected according to circular systematic sampling as for as possible from each of the four periods as stated above.
The Libertad Project is an early stage gold-silver epithermal vein and stockwork system identified over 1.8 kms in length that previously had no systematic sampling and has never been drilled.
Densities of mussels were quantified using a systematic sampling design with three random starts.
The systematic sampling of south Luangwa's archaeological treasures has produced a wealth of artefacts, ranging from early stone tools to pottery which is just a few hundred years old.
Systematic sampling typically involves sorted data such as accounting records filed by date or medical records filed alphabetically.
"I'm also eager to advance the development of a network of global ocean observatories to enable systematic sampling of the oceans and to provide much-needed input for data-driven policy decisions," she said.
The author supplements other works on this topic by providing the words for a large and systematic sampling of temperance songs.
Because we did not do systematic sampling, our results cannot address the prevalence and distribution of R.

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