Educational Psychology, University of Nebraska-Lincoln, NE, USA.
Eval Health Prof. 2021 Dec;44(4):416-427. doi: 10.1177/01632787211024356. Epub 2021 Jun 18.
Although the bias-corrected (BC) bootstrap is an often-recommended method for testing mediation due to its higher statistical power relative to other tests, it has also been found to have elevated Type I error rates with small sample sizes. Under limitations for participant recruitment, obtaining a larger sample size is not always feasible. Thus, this study examines whether using alternative corrections for bias in the BC bootstrap test of mediation for small sample sizes can achieve equal levels of statistical power without the associated increase in Type I error. A simulation study was conducted to compare Efron and Tibshirani's original correction for bias, , to six alternative corrections for bias: (a) mean, (b-e) Winsorized mean with 10%, 20%, 30%, and 40% trimming in each tail, and (f) medcouple (robust skewness measure). Most variation in Type I error (given a medium effect size of one regression slope and zero for the other slope) and power (small effect size in both regression slopes) was found with small sample sizes. Recommendations for applied researchers are made based on the results. An empirical example using data from the ATLAS drug prevention intervention study is presented to illustrate these results. Limitations and future directions are discussed.
虽然偏置校正（BC）自举是一种常用于测试中介效应的方法，因为它相对于其他测试具有更高的统计功效，但也发现它在小样本量下会出现升高的Ⅰ类错误率。在参与者招募的限制下，获得更大的样本量并不总是可行的。因此，本研究探讨了在小样本量下，使用替代的偏置校正方法对 BC 自举中介效应检验是否可以在不增加Ⅰ类错误的情况下实现相等的统计功效。进行了一项模拟研究，以比较 Efron 和 Tibshirani 原始的偏置校正 ，与六种替代的偏置校正方法：（a）均值，（b-e）带有 10%、20%、30%和 40%尾部修剪的 Winsorized 均值，以及（f）medcouple（稳健偏度度量）。在小样本量下，Ⅰ类错误（给定一个回归斜率的中等效应大小，另一个斜率为零）和功效（两个回归斜率的小效应大小）的变化最大。根据结果为应用研究人员提出了建议。使用 ATLAS 药物预防干预研究的数据呈现了一个实证示例，以说明这些结果。讨论了局限性和未来方向。
