Explanation of Two Anomalous Results in Statistical Mediation Analysis.
Explanation of Two Anomalous Results in Statistical Mediation Analysis.
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DOI：
10.1080/00273171.2012.640596
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发表时间：
2012
影响因子：
3.8
通讯作者：
Mackinnon DP
中科院分区：
文献类型：
--
作者：
Fritz MS;Taylor AB;Mackinnon DP
以往对不同中介模型检验方法的研究一致发现了两个异常结果。第一个结果是，在非重新采样测试或不包括偏差校正的重新采样测试中没有发现经过偏差校正和加速偏差校正的自举测试的第一类错误率升高。这是一个特别值得关注的问题，因为与其他测试相比，偏差校正自举法的统计能力更高，因此经常被推荐和使用。第二个结果是统计能力达到远低于1.0的渐近线，在某些情况下，随着X与M之间关系的大小增加，统计能力甚至略有下降。为了更详细地检验这些发现，进行了两次计算机模拟。第一次模拟的结果发现，偏校正和加速偏校正bootstrap的I型错误率增加是构成中介效应的单个路径大小与样本量之间相互作用的函数，因此，当样本量较小，非零路径的效应大小为中等或更大时，I型错误率会升高。第二次模拟的结果发现，当M和Y之间的路径b很小时，作为a路径效应大小的函数，统计功率的停滞和下降主要发生。本文利用针对高中足球运动员的类固醇预防和健康促进项目（运动员训练和学习避免类固醇）的数据提供了两个实证中介例子，一个例子说明了偏差校正引导测试中可能出现的I型错误，另一个例子说明了与a的大小相关的力量损失。本文讨论了这些发现的含义。
Previous studies of different methods of testing mediation models have consistently found two anomalous results. The first result is elevated Type I error rates for the bias-corrected and accelerated bias-corrected bootstrap tests not found in nonresampling tests or in resampling tests that did not include a bias correction. This is of special concern as the bias-corrected bootstrap is often recommended and used due to its higher statistical power compared with other tests. The second result is statistical power reaching an asymptote far below 1.0 and in some conditions even declining slightly as the size of the relationship between X and M, a, increased. Two computer simulations were conducted to examine these findings in greater detail. Results from the first simulation found that the increased Type I error rates for the bias-corrected and accelerated bias-corrected bootstrap are a function of an interaction between the size of the individual paths making up the mediated effect and the sample size, such that elevated Type I error rates occur when the sample size is small and the effect size of the nonzero path is medium or larger. Results from the second simulation found that stagnation and decreases in statistical power as a function of the effect size of the a path occurred primarily when the path between M and Y, b, was small. Two empirical mediation examples are provided using data from a steroid prevention and health promotion program aimed at high school football players (Athletes Training and Learning to Avoid Steroids), one to illustrate a possible Type I error for the bias-corrected bootstrap test and a second to illustrate a loss in power related to the size of a. Implications of these findings are discussed.
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