A comparison of binary models dealing with an extraneous effect relating to the main risk factor, but not relating to the outcome variable.

Full Abstract

In a binary model relating a response variable Y to a risk factor X, account may need to take of an extraneous effect Z that is related to X, but not Y. This is known as the association pattern Y-X-Z. The extraneous variable Z is commonly included in models as a covariate. This paper concerns binary models, and investigates the use of deviation from the group mean (D-GM) and deviation from the fitted fractional polynomial value (D-FP) for removing the extraneous effect of Z.In a simulation study, D-FP performed excellently, while the performance of D-GM was slightly worse than the traditional method of treating Z as a covariate. In addition, estimators with excessive mean square errors or standard errors cannot occur when D-GM or D-FP is employed, even in small or sparse data sets.The Y-X-Z association pattern studied here often occurs in fetal studies, where the fetal measurement (X) varies with the gestation age (Z), but gestation age does not relate to the outcome variable (Y; e.g. Down's syndrome). D-GM and D-FP perform well with illustrative data from fetal studies, although there is a weak association between X and Z with a lower proportion of case subjects (e.g. 11:1, control to case).It is not necessary to add a new covariate when a model deals with the extraneous effect. The D-FP or D-GM methods perform well with the real data studied here, and moreover, D-FP demonstrated excellent performance in simulations. Copyright (c) 2009 John Wiley & Sons, Ltd.

Author information

Author/s: Fu, Chong Yau (CY); Yang, Ya-Wen (YW);

Affiliation: Division of Biostatistics, Institute of Public Health, National Yang-Ming University, Taipei, Taiwan. chong(-atsign-)ym.edu.tw

Journal and publication information

Publication Type: Comparative Study; Evaluation Studies; Journal Article; Research Support, Non-U.S. Gov't

Journal: Statistics in medicine (Stat Med), published in England. (Language: eng)

Reference: 2009-May; vol 28 (issue 10) : pp 1473-86

Dates: Created 2009/04/13; Completed 2009/07/01; Revised 2009/07/17;

PMID: 19243085, status: MEDLINE (last retrieval date: 7/25/2009, IMS Date: 25 Jul 2009 00:00:00)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

External Links for this article
(including full text providers, if available):

Click Electronic Full-text Provider Links to see options for finding the electronic full text links to this article. Note there may be a subscription or fee required for access to the full text. See our FAQ for information on finding FREE full text articles.

This article may also be located in paper journal collections available in many libraries. Use the Journal and Publication Information above to find the full article.