a Department of Epidemiology and Biostatistics , Case Western Reserve University .
Multivariate Behav Res. 2008 Apr-Jun;43(2):268-88. doi: 10.1080/00273170802034877.
In behavioral research, interest is often in examining the degree to which the effect of an independent variable X on an outcome Y is mediated by an intermediary or mediator variable M. This article illustrates how generalized estimating equations (GEE) modeling can be used to estimate the indirect or mediated effect, defined as the amount by which the regression coefficient of X on Y changes after adjusting for M. Advantages of this method are: (a) it applies to the class of generalized linear models, including linear, logistic, and Poisson regression as special cases; (b) it allows multiple independent variables and mediators in the same model; and (c) asymptotically valid standard errors and confidence intervals are obtained using standard software. This methodology is compared with the bootstrap, another general methodology that can be applied to the same broad class of models, and is evaluated using simulation in both linear and logistic regression scenarios. The methods are utilized to examine the degree to which the effect of low birthweight status on internalizing symptoms at age 20 is mediated through IQ at age 8.
在行为研究中，人们通常感兴趣的是检验自变量 X 对因变量 Y 的影响程度有多大是由中介或中介变量 M 介导的。本文说明了如何使用广义估计方程 (GEE) 模型来估计间接或中介效应，该效应定义为在调整 M 后 X 对 Y 的回归系数变化的量。这种方法的优点是：(a) 它适用于广义线性模型的类别，包括线性、逻辑和泊松回归作为特例；(b) 它允许在同一个模型中包含多个自变量和中介变量；(c) 使用标准软件可以获得渐近有效的标准误差和置信区间。该方法与 bootstrap 进行了比较，bootstrap 是另一种可以应用于同一广泛模型类别的通用方法，并在线性和逻辑回归场景中通过模拟进行了评估。该方法用于检验低出生体重状态对 20 岁时内化症状的影响有多大是通过 8 岁时的智商来介导的。
