Abstract
Sampling from medical records is a classical technique in medical and epidemiologic research. Let us look at a fictitious example from the pre-computer age. Suppose Dr. Q. wants to find the frequency of a risk factor A among all patients who were treated in a given ward of his hospital during the period 1950–1959. There had been N = 9850 such patients, and for every one of them a medical record in the form of a file exists where the presence or absence of A is recorded. Dr. Q. could look through the whole (dust covered) set of files and count the occurrence of A in it. Suppose that he finds it 271 times; this would be the “frequency” he is looking for. The so-called “relative frequency”, or “proportion”, of A is more instructive; it is equal to
Sampling is the art of obtaining information on a target population by studying only a suitably chosen subpopulation. The latter is called a sample or a study population . The information includes a description of the error committed by using only a sample. Almost every epidemiologic study involves sampling, but sampling may also be performed regularly within a given information system.
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Krickeberg, K., Van Trong, P., Thi My Hanh, P. (2019). The Origin of Information: Sampling. In: Epidemiology. Statistics for Biology and Health. Springer, Cham. https://doi.org/10.1007/978-3-030-16368-6_12
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DOI: https://doi.org/10.1007/978-3-030-16368-6_12
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