Population, Sample, or…?
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Population, Sample, or…? book
Modern epidemiology concerns itself with the study of disease in the living; the unit of study is a population that, for example, might be all the women in South Wales, workers in a factory, children in primary schools in Manchester. A closed population rarely occurs outside the mind of an epidemiologist or a demographer, but it does form the basis for the calculation of life tables. By contrast, an open population permits loss and gain in number through the agency of births, deaths, immigration, and emigration. While discussing the differences between archaeological assemblages and the populations with which modern epidemiologists generally choose to work, one must mention time scales. In modern practice, samples for epidemiological study are typically drawn at random. The methods employed in drawing a random sample vary, but they should ensure that – in theory, at least – each member of the population has an equal chance of being selected.