title: [Different selection rates--fallacies in epidemiological studies].
abstract: Practical examples from preventive and curative medicine are given to demonstrate how competing selection rates distort the results of epidemiological studies. In order to quantify this distorsion the bias is tabulated and graphed for different combinations of features (diseases, symptoms, findings, etc.) on the one hand and different admission or participation rates on the other hand. With the help of a formula which can be stored in a pocket calculator the sample bias can be quantified also. Prerequisite is the estimation of selection rates. They have such a bearing on the results of epidemiological studies that it is advisable to ask two questions before any interpretation: 1. which factors can lead to different admission rates in the groups (A,B) under study and 2. which factors can lead to different admission rates of persons with and without the feature (X) under study.
mesh_terms: D001195:Asbestosis; D003327:Coronary Disease; D004812:Epidemiologic Methods; D005260:Female; D006305:Health Status Indicators; D006306:Health Surveys; D006801:Humans; D008175:Lung Neoplasms; D008297:Male; D008403:Mass Screening; D008962:Models, Theoretical; D009784:Occupational Diseases; D012306:Risk
vernacular_title: Unterschiedliche Selektionsraten--falsche Schlüsse bei epidemiologischen Untersuchungen.