Cluster sample | Article about cluster sample by The Free Dictionary
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cluster sample a method of SAMPLING which selects from groups (clusters) existing in the parent population, rather than assembling a RANDOM SAMPLE. This tends to be quicker and cheaper, but may lead to a BIASED SAMPLE if the clusters are not representative of the parent population. For example, polls taken of attitudes to government policy may be carried out in selected areas of the country thought to be representative, but, because of local political dynamics, this may not be the case.