Rijnhart Judith J M, Valente Matthew J, MacKinnon David P
College of Public Health, University of South Florida.
Department of Psychology, Arizona State University.
Multivariate Behav Res. 2025 Mar-Apr;60(2):296-304. doi: 10.1080/00273171.2024.2418515. Epub 2024 Oct 29.
Despite previous warnings against the use of the difference-in-coefficients method for estimating the indirect effect when the outcome in the mediation model is binary, the difference-in-coefficients method remains readily used in a variety of fields. The continued use of this method is presumably because of the lack of awareness that this method conflates the indirect effect estimate and non-collapsibility. In this paper, we aim to demonstrate the problems associated with the difference-in-coefficients method for estimating indirect effects for mediation models with binary outcomes. We provide a formula that decomposes the difference-in-coefficients estimate into (1) an estimate of non-collapsibility, and (2) an indirect effect estimate. We use a simulation study and an empirical data example to illustrate the impact of non-collapsibility on the difference-in-coefficients estimate of the indirect effect. Further, we demonstrate the application of several alternative methods for estimating the indirect effect, including the product-of-coefficients method and regression-based causal mediation analysis. The results emphasize the importance of choosing a method for estimating the indirect effect that is not affected by non-collapsibility.
尽管之前有警告指出，当中介模型中的结果为二元变量时，使用系数差异法来估计间接效应存在问题，但系数差异法仍在各个领域被广泛使用。这种方法持续被使用，大概是因为人们没有意识到该方法混淆了间接效应估计和不可折叠性。在本文中，我们旨在展示在具有二元结果的中介模型中，使用系数差异法估计间接效应所存在的问题。我们提供了一个公式，将系数差异估计分解为：（1）不可折叠性估计，以及（2）间接效应估计。我们通过模拟研究和实证数据示例来说明不可折叠性对间接效应系数差异估计的影响。此外，我们展示了几种估计间接效应的替代方法的应用，包括系数乘积法和基于回归的因果中介分析。结果强调了选择一种不受不可折叠性影响的间接效应估计方法的重要性。
