Statistical properties of four effect-size measures for mediation models.
This project examined the performance of classical and Bayesian estimators of four effect size measures for the indirect effect in a single-mediator model and a two-mediator model. Compared to the proportion and ratio mediation effect sizes, standardized mediation effect-size measures were relatively unbiased and efficient in the single-mediator model and the two-mediator model. Percentile and bias-corrected bootstrap interval estimates of ab/sY, and ab(sX)/sYin the single-mediator model outperformed interval estimates of the proportion and ratio effect sizes in terms of power, Type I error rate, coverage, imbalance, and interval width. For the two-mediator model, standardized effect-size measures were superior to the proportion and ratio effect-size measures. Furthermore, it was found that Bayesian point and interval summaries of posterior distributions of standardized effect-size measures reduced excessive relative bias for certain parameter combinations. The standardized effect-size measures are the best effect-size measures for quantifying mediated effects.
Department of Psychology, Arizona State University, 950 S. McAllister Ave, Tempe, AZ, 85287, USA. mmiocevi@asu.edu.
Milica
M
Miočević
Department of Psychology, Arizona State University, 950 S. McAllister Ave, Tempe, AZ, 85287, USA.
Holly P
HP
O'Rourke
Department of Psychology, Arizona State University, 950 S. McAllister Ave, Tempe, AZ, 85287, USA.
David P
DP
MacKinnon
Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
Hendricks C
HC
Brown
D001499:Bayes Theorem; D015982:Bias; D003198:Computer Simulation; D006801:Humans; D015233:Models, Statistical; D017008:Negotiating; D018401:Sample Size
Bayesian methods; Bias; Effect sizes; Efficiency; Interval estimates; Mediation