title: Classification, direction, and prevention of bias in epidemiologic research.
abstract: We describe an extension of an existing framework used by several investigators for classifying various types of bias. The framework consists of three categories of bias: selection, information, and confounding. The existing framework is expanded to include subclassification according to the type of study design: cross-sectional, case-control, retrospective cohort, and prospective cohort. Direction and method of prevention of biases within each category in the framework are discussed. This article provides a useful checklist for epidemiologists to determine possible sources and methods of reduction of bias that are specific to a particular type of study design.
authors.affiliation: Occupational and Environmental Health Unit, Faculty of Medicine, University of Toronto, Ontario, Canada.
authors.forename: B C
authors.initials: BC
authors.lastname: Choi
authors.forename: A L
authors.initials: AL
authors.lastname: Noseworthy
mesh_terms: D015982:Bias; D004813:Epidemiology; D006801:Humans; D015588:Observer Variation; D011315:Preventive Medicine; D012107:Research Design; D015983:Selection Bias