Hey,
For my thesis I am conducting a meta-analysis.
I find it difficult to interpret this funnel plot. It looks symmetrical but there is a underpresentation of studies with a high SE and/or low SE (all around the same sample sizes).
Can this explain something about publication bias?
Thank you so much for the help.
Kind Regards,
Laura
I am not sure that this funnel plot looks summetrical; the triangle's left corner has 3 studies, as opposed to 0 on the right side. Bear also in mind that sample sizes and methodological qualities also affect the symmetry of a funnel plot. You could possibly explain this due to the effect sizes (as seen in the forest plot) and sample sizes.
However, since funnel plots are subjective. i would recommend trying another, objective method for assessing the publication bias, such as Harbord's modified test (Article A modified test for small-study effects in meta-analyses of ...
).
The right column has a gradual trend from positive to negative with relatively small error bars. It may not be the bias issue but the issue is the averages obtained by the studies. It looks like that is the reason some studies are outside of the triangle. Just my thought.
its looks symmetrical to me, if you're not sure, do the Egger's test, it will show you if there a possible publication bias or not, the results from both tests will confirm that.
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