The term “funnel plot” comes from the fact that as study size increases, the precision of the estimated intervention effect also increases. This results in a wider scatter of estimates at the bottom (smaller studies) and a narrower spread at the top (larger studies), forming an inverted funnel shape when no bias is present.
Q & A Forum
Meta Analysis
Q: Why is it called a "funnel plot"?
The term “funnel plot” comes from the fact that as study size increases, the precision of the estimated intervention effect also increases. This results in a wider scatter of estimates at the bottom (smaller studies) and a narrower spread at the top (larger studies), forming an inverted funnel shape when no bias is present.
Refernce:
Cochrane Handbook for Systematic Reviews of Interventions. (2011). 10.4.1 Funnel plots. The Cochrane Collaboration. Retrieved from https://handbook-5-1.cochrane.org/chapter_10/10_4_1_funnel_plots.htm