abstract:A funnel plot is a useful graph designed to check the existence of publication bias in systematic reviews and meta-analyses. It assumes that the largest studies will be near the average, and small studies will be spread on both sides of the average.
In addition, thefunnelplot for assessingriskofbiasappearedtobe asymmetrical; suggesting thatsmallstudieswith 'negative' results are lesslikely to be published.