This is the program for the 2010 Joint Statistical Meetings in Vancouver, British Columbia.

Abstract Details

Activity Number: 71
Type: Contributed
Date/Time: Sunday, August 1, 2010 : 4:00 PM to 5:50 PM
Sponsor: Section on Statistics in Epidemiology
Abstract - #309252
Title: Examining the Bias of the Difference in Coefficients Method for Evaluating Intermediate Endpoints Using Logistic Regression
Author(s): Miranda Elaine Kroehl*+ and Lorraine Ogden
Companies: University of Colorado, Denver and University of Colorado, Denver
Address: , , ,
Keywords: Intermediate Endpoint ; Mediator ; Mediation ; Difference in Coefficients ; Product of Coefficients

The evaluation of intermediate endpoints (IE) is becoming increasingly popular in both clinical and epidemiological research. Two common methods are often used for estimating the IE effect: the product of coefficients method and the difference in coefficients method. It has been noted that the point estimates from these two methods are not usually equal for binary outcome data, however, the magnitude of this discrepancy has not been well described. This paper states the conditions under which the difference in coefficient method is biased when using logistic regression. For instance, (1) the estimate is usually biased towards no effect when a true IE effect exists; (2) the magnitude of the bias increases with increasing strength of association between the IE and the outcome; and (3) the bias is negligible when the outcome is rare.

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