title: Causation, bias and confounding: a hitchhiker's guide to the epidemiological galaxy Part 2. Principles of causality in epidemiological research: confounding, effect modification and strength of association.
authors.affiliation: Department of Epidemiology, University of Cape Town, Cape Town, South Africa. samshap@mweb.co.za
authors.forename: Samuel
authors.initials: S
authors.lastname: Shapiro
mesh_terms: D015982:Bias; D015984:Causality; D015986:Confounding Factors, Epidemiologic; D015340:Epidemiologic Research Design; D016021:Epidemiologic Studies; D006801:Humans; D018570:Risk Assessment