Bauer Daniel J, Preacher Kristopher J, Gil Karen M
Department of Psychology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3270, USA.
Psychol Methods. 2006 Jun;11(2):142-63. doi: 10.1037/1082-989X.11.2.142.
The authors propose new procedures for evaluating direct, indirect, and total effects in multilevel models when all relevant variables are measured at Level 1 and all effects are random. Formulas are provided for the mean and variance of the indirect and total effects and for the sampling variances of the average indirect and total effects. Simulations show that the estimates are unbiased under most conditions. Confidence intervals based on a normal approximation or a simulated sampling distribution perform well when the random effects are normally distributed but less so when they are nonnormally distributed. These methods are further developed to address hypotheses of moderated mediation in the multilevel context. An example demonstrates the feasibility and usefulness of the proposed methods.
作者提出了在所有相关变量均在第1层进行测量且所有效应均为随机效应的情况下，评估多层次模型中直接效应、间接效应和总效应的新程序。给出了间接效应和总效应的均值、方差以及平均间接效应和总效应的抽样方差的公式。模拟结果表明，在大多数情况下，估计值是无偏的。当随机效应呈正态分布时，基于正态近似或模拟抽样分布的置信区间表现良好，但当随机效应呈非正态分布时，表现则较差。这些方法被进一步拓展，以处理多层次背景下的调节中介假设。一个例子展示了所提出方法的可行性和实用性。
