Observational Studies - AMA Manual of Style

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Observational Studies 

Study Design and Statistics

Margaret A. Winker

and Stephen J. Lurie

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PRINTED FROM AMA MANUAL OF STYLE ONLINE (www.amamanualofstyle.com). © American Medical Association, 2009. All Rights Reserved. Under the terms of the license agreement, an individual user may print out a PDF of a single chapter of a title in AMA Manual of Style Online for personal use (for details see Privacy Policy). date: 24 November 2015

In an observational study, the researcher identifies a condition or outcome of interest and then measures factors that may be related to that outcome. Although observational studies cannot lead to strong causal inferences, they may nonetheless suggest certain causal hypotheses. To infer causation in observational studies, investigators attempt to establish a sequence of events if event A generally precedes event B in time, then it is possible that A may be responsible for causing B. Such studies may be either (the investigator tries to reconstruct what happened in the past) or prospective (the investigator identifies a group of individuals and

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