Each week, we select a recently published Open Access article to feature. This week’s article comes from Statistica Neerlandica and extends the partial posterior p value  to test multilevel mediation.

The article’s abstract is given below, with the full article available to read here.

Cox, K., & Kelcey, B. (2023). A partial posterior p value test for multilevel mediation. Statistica Neerlandica, 1– 21. https://doi.org/10.1111/stan.12291

A variety of inferential tests are available for single and multilevel mediation but most come with notable limitations that balance tradeoffs between power and Type I error. We extend the partial posterior p value method (p₃ method) to test multilevel mediation. This contemporary resampling-based composite approach is specifically suited for complex null hypotheses. We develop the p₃ method and investigate its performance within the context of two-level cluster-randomized multilevel mediation studies. Similar to its performance in single-level studies, we found that the p₃ method performed well relative to other mediation tests suggesting it provides a judicious balance between Type I error rate and power. While bias-corrected bootstrapping achieved the best overall performance, the p₃ method serves as an alternative tool for researchers investigating multilevel mediation that is especially useful when conducting a priori power analyses. To encourage utilization, we provide R code for implementing the p₃ method.