Fig. 5

Publication bias. This figure is used to investigate the publication bias of studies. Circles show selected studies, and the area of each circle is equivalent to the weight of each study. The horizontal axis represents accuracy, and the vertical axis represents the standardized effect. The line shown in this figure is a regression line related to Egger’s regression test. It shows that whether this line cut the vertical axis at the point near zero or not. If this line distance from zero, it indicates a bias in publishing the results. If there is no publication bias, it is expected that this line passes from origin to a point near the origin. Since intercept (width from origin) is close to 9 in this figure, we conclude that publication bias is significant. Two diamonds that are plotted on the vertical axis indicate confidence interval corresponds to the coefficient obtained from the regression test β_1 that it is 4.2 to 14.1. Because zero is not included in the confidence interval. Therefore, it could be concluded that the publication bias is significant