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).