title: Meta-analysis of multiple outcomes: a multilevel approach.
abstract: In meta-analysis, dependent effect sizes are very common. An example is where in one or more studies the effect of an intervention is evaluated on multiple outcome variables for the same sample of participants. In this paper, we evaluate a three-level meta-analytic model to account for this kind of dependence, extending the simulation results of Van den Noortgate, López-López, Marín-Martínez, and Sánchez-Meca Behavior Research Methods, 45, 576-594 (2013) by allowing for a variation in the number of effect sizes per study, in the between-study variance, in the correlations between pairs of outcomes, and in the sample size of the studies. At the same time, we explore the performance of the approach if the outcomes used in a study can be regarded as a random sample from a population of outcomes. We conclude that although this approach is relatively simple and does not require prior estimates of the sampling covariances between effect sizes, it gives appropriate mean effect size estimates, standard error estimates, and confidence interval coverage proportions in a variety of realistic situations.
authors.affiliation: Faculty of Psychology and Educational Sciences and itec-iMinds, University of Leuven, Vesaliusstraat 2, 3000, Leuven, Belgium. wim.vandennoortgate@kuleuven-kortrijk.be.
authors.forename: Wim
authors.initials: W
authors.lastname: Van den Noortgate
authors.affiliation: School of Social and Community Medicine, University of Bristol, Bristol, UK.
authors.forename: José Antonio
authors.initials: JA
authors.lastname: López-López
authors.affiliation: Faculty of Psychology, Universidad de Murcia, Murcia, Spain.
authors.forename: Fulgencio
authors.initials: F
authors.lastname: Marín-Martínez
authors.affiliation: Faculty of Psychology, Universidad de Murcia, Murcia, Spain.
authors.forename: Julio
authors.initials: J
authors.lastname: Sánchez-Meca
mesh_terms: D003198:Computer Simulation; D003627:Data Interpretation, Statistical; D006801:Humans; D015201:Meta-Analysis as Topic; D012015:Reference Standards; D018401:Sample Size; D012494:Sampling Studies; D016896:Treatment Outcome
keywords: Dependence; Meta-analysis; Multilevel; Multiple outcomes