Assessing Publication Bias

Three methods of assessing publication bias were used in this study: the funnel plot, the Egger’s test, and the Begg and Mazumdar correlation test. The funnel plot is a visual representation, which is based on the fact that in the absence of publication bias, the mean effect size is expected to be the same in small and in large studies (Hunter & Schmidt, 2015). The Egger’s test is a parametric test that assesses the funnel plot asymmetry, and is based on linear regression analysis. A significant t-test result indicates that publication bias may exist. Finally, the Begg and Mazumdar’s test is a nonparametric correlation test, which assesses whether or not there is a relationship between the study size and effect size (Vevea et al., 2019).