title: A positive or a negative confounding variable? A simple teaching aid for clinicians and students.
abstract: Anticipating the direction of a confounding variable can be problematic especially to introductory students. Using elementary rules of mathematics, we describe below a simple instructional tool for deriving the direction of confounding bias. The tool is illustrated with examples and a heuristic mathematical justification is also described.
authors.affiliation: Department of Epidemiology and Population Health, Faculty of Health Sciences, American University of Beirut, Beirut, Lebanon. ansibai@aub.edu.lb
authors.forename: Abla
authors.initials: A
authors.lastname: Mehio-Sibai
authors.forename: Manning
authors.initials: M
authors.lastname: Feinleib
authors.forename: Tarek A
authors.initials: TA
authors.lastname: Sibai
authors.forename: Haroutune K
authors.initials: HK
authors.lastname: Armenian
mesh_terms: D015982:Bias; D015986:Confounding Factors, Epidemiologic; D004813:Epidemiology / Q000193:education*; D007861:Lebanon; D015233:Models, Statistical; D010820:Physicians; D013337:Students, Medical