What is the purpose of creating a funnel plot when assessing against potential publication bias?
The purpose of creating a funnel plot when assessing against potential publication bias is to identify any potential bias in the literature. A funnel plot is a graphical representation of the effect size (measured as the risk ratio or odds ratio) plotted against the standard error of the effect size. It is used to identify any potential biases in the literature, such as publication bias, where studies with smaller sample sizes and lower statistical power tend to show larger effect sizes than those with larger sample sizes and higher statistical power. If there is no publication bias, the points should form a symmetrical funnel shape. If there is publication bias, there will be an asymmetrical funnel shape, with the smaller studies tending to show larger effect sizes than the larger studies.