A positive or a negative confounding variable? A simple teaching aid for clinicians and students

Ann Epidemiol. 2005 Jul;15(6):421-3. doi: 10.1016/j.annepidem.2004.10.004. Epub 2005 Jan 21.


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.

MeSH terms

  • Bias*
  • Confounding Factors, Epidemiologic*
  • Epidemiology / education*
  • Lebanon
  • Models, Statistical
  • Physicians*
  • Students, Medical*