Abstract
Conditional process models, including moderated mediation models and mediated moderation models, are widely used in behavioral science research. However, few studies have examined approaches to conduct statistical power analysis for such models and there is also a lack of software packages that provide such power analysis functionalities. In this paper, we introduce new simulation-based methods for power analysis of conditional process models with a focus on moderated mediation models. These simulation-based methods provide intuitive ways for sample-size planning based on regression coefficients in a moderated mediation model as well as selected variance and covariance components. We demonstrate how the methods can be applied to five commonly used moderated mediation models using a simulation study, and we also assess the performance of the methods through the five models. We implement our approaches in the WebPower R package and also in Web apps to ease their application.
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Notes
Models 7 and 8 in Hayes (2017) correspond to Model 2 in Panel B of Figure 2 in Preacher et al. (2007), Model 14 and 15 in Hayes (2017) correspond to Model 3 in Panel C in Preacher et al. (2007), and Model 58 in Hayes (2017) correspond to Model 5 in Panel E in Preacher et al. (2007). We will address the models using notations from Hayes (2017) in this paper.
We have conducted a small scale simulation with the number of replications up to 1000 and found little difference in the results. Therefore, we decided to use 100 for the sake of computing time.
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Acknowledgements
This work was supported by grants from the Department of Education (R305D140037; R305D210023). However, the contents do not necessarily represent the policy of the Department of Education, and you should not assume endorsement by the federal government. It was also partially supported by an award from the Notre Dame International at the University of Notre Dame. The code used in this study is available on GitHub and CRAN, and the study was not preregistered. Simulation data are not included.
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Correspondence concerning this article should be addressed to Ziqian Xu (zxu9@nd.edu), Wen Qu (wqu@fudan.edu.cn), and Zhiyong Zhang (zzhang4@nd.edu).
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Xu, Z., Gao, F., Fa, A. et al. Statistical power analysis and sample size planning for moderated mediation models. Behav Res (2024). https://doi.org/10.3758/s13428-024-02342-2
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DOI: https://doi.org/10.3758/s13428-024-02342-2