© 1995 by Biometrika Trust
MISCELLANEA |
A note on the bias due to omitted confounders
Division of Statistics, University of California Davis, California 95616, U. S. A
Received for publication 1 November 1992.
Revision received 1 December 1994.
| Abstract |
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In observational studies some confounders may be unknown and therefore omitted from the analysis while others are adjusted for. Approximations to the functions defining the relationship between the parameters in the full and reduced models are proposed leading to asymptotic bias estimates. Numerical calculations for logistic and Poisson regression models show good agreement between asymptotic and simulation bias. A data set containing the relationship between low birth weight and smoking (Hosmer & Lemeshow, 1989) is used as an illustration.
Key Words: Bias Confounding Generalised linear model Omitted covariates