Sampling stuff (1)

Sampling stuff (1) - Sampling stuff Cluster sampling is a...

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Sampling stuff: Cluster sampling is a sampling technique used when "natural" groupings are evident in a statistical population . It is often used in marketing research. In this technique, the total population is divided into these groups (or clusters) and a sample of the groups is selected. Then the required information is collected from the elements within each selected group. This may be done for every element in these groups or a subsample of elements may be selected within each of these groups. The technique works best when most of the variation in the population is within the groups, not between them. In statistics , stratified sampling is a method of sampling from a population. When sub-populations vary considerably, it is advantageous to sample each subpopulation (stratum) independently. Stratification is the process of grouping members of the population into relatively homogeneous subgroups before sampling. The strata should be mutually exclusive: every element in the population must be assigned to only one stratum. The strata should also be collectively exhaustive: no population element can be excluded. Then random or systematic sampling is applied within each stratum. This often improves the representativeness of the sample by reducing sampling error. It can produce a weighted mean that has less variability than the arithmetic mean of a simple random sample of the population.
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Sampling stuff (1) - Sampling stuff Cluster sampling is a...

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