Funnel Plots

Question 1

What is the primary purpose of funnel plots?

Answer 1

To demonstrate the existence of publication bias in meta-analyses.

Question 2

What does a symmetrical, inverted funnel shape indicate?

Answer 2

There is unlikely to be publication bias.

Question 3

What does an asymmetrical funnel indicate?

Answer 3

A relationship between treatment effect and study size. This indicates either publication bias or the “small study effect” -a systemic difference between smaller and larger studies.