A funnel plot in a meta-analysis shows marked asymmetry with fewer small studies on the left side. The MOST likely explanation is:
- A Publication bias — small studies with negative results are not published ✓
- B All included studies have high methodological quality
- C The pooled effect size is not significant
- D High statistical power in all studies
Correct answer: A. Publication bias — small studies with negative results are not published
Explanation
A symmetric funnel plot indicates no publication bias. Asymmetry — particularly absence of small studies on one side — suggests publication bias, where small studies with negative (non-significant) results are less likely to be published, while small studies with large positive effects are more likely to be published. Egger's test or Begg's test can formally assess funnel plot asymmetry.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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