Abstract
That conditioning on a common effect of exposure and outcome may cause selection, or collider-stratification, bias is not intuitive. We provide two hypothetical examples to convey concepts underlying bias due to conditioning on a collider. In the first example, fever is a common effect of influenza and consumption of a tainted egg-salad sandwich. In the second example, case-status is a common effect of a genotype and an environmental factor. In both examples, conditioning on the common effect imparts an association between two otherwise independent variables; we call this selection bias.
Original language | English (US) |
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Article number | dyp334 |
Pages (from-to) | 417-420 |
Number of pages | 4 |
Journal | International journal of epidemiology |
Volume | 39 |
Issue number | 2 |
DOIs | |
State | Published - Apr 2010 |
Bibliographical note
Funding Information:Grants R03-AI-071763, R01-AA-01759 and P30-AI-50410 (to S.R.C.); Lineberger Cancer Center Core Grant CA16086 and P30-AI-50410 (to H.C.); Intramural Research Program of the Eunice Kennedy Shriver NICHD, NIH; and the American Chemical Council to (to E.S.); P30-ES-10126 (to C.P.).