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A case–control study (also known as case–referent study) is a type of observational study in which two existing groups differing in outcome are identified and compared on the basis of some supposed causal attribute.
A nested case–control (NCC) study is a variation of a case–control study in which cases and controls are drawn from the population in a fully enumerated cohort. [1] Usually, the exposure of interest is only measured among the cases and the selected controls. Thus the nested case–control study is more efficient than the full cohort design.
Epidemiological (and other observational) studies typically highlight associations between exposures and outcomes, rather than causation. While some consider this a limitation of observational research, epidemiological models of causation (e.g. Bradford Hill criteria) [7] contend that an entire body of evidence is needed before determining if an association is truly causal. [8]
Level II1: Evidence from at least one well designed cohort study or case control study, preferably from more than one center or research group. Level II2: Comparisons between times and places with or without the intervention; Level III: Opinions of respected authorities, based on clinical experience, descriptive studies or reports of expert ...
While retrospective cohort studies try to compare the risk of developing a disease to some already known exposure factors, a case-control study will try to determine the possible exposure factors after a known disease incidence. Both the relative risk and odds ratio are relevant in retrospective cohort studies, but only the odds ratio can be ...
When choosing a study design, many factors must be taken into account. Different types of studies are subject to different types of bias. For example, recall bias is likely to occur in cross-sectional or case-control studies where subjects are asked to recall exposure to risk factors. Subjects with the relevant condition (e.g. breast cancer ...
The choice of how to group participants depends on the research hypothesis and on how the participants are sampled.In a typical experimental study, there will be at least one "experimental" condition (e.g., "treatment") and one "control" condition ("no treatment"), but the appropriate method of grouping may depend on factors such as the duration of measurement phase and participant ...
Having demonstrated the power of cohort studies, Lane-Claypon went on to develop another key type of epidemiological investigation, the case-control study. [8] Lane-Claypon tracked down 500 women with a history of breast cancer – the "cases" – and compared them with 500 women who were free of the disease but otherwise broadly similar, known ...