In the forest plot accompanying a meta-analysis, small studies cluster away from the vertical line of no effect while large studies cluster symmetrically near it, producing a visibly asymmetric funnel shape. The most appropriate interpretation of this finding is:
- A Publication bias, with small studies showing negative results remaining unpublished ✓
- B High statistical heterogeneity requiring a random effects model
- C A large pooled treatment effect that is highly significant
- D Adequate methodological quality of the included trials
Correct answer: A. Publication bias, with small studies showing negative results remaining unpublished
Explanation
In the absence of bias, study estimates scatter symmetrically around the pooled effect, with precision widening as sample size falls. Asymmetry, typically due to small studies with unfavourable or non-significant results going unpublished, signals publication bias or related small-study effects. Heterogeneity is assessed by the Cochran Q statistic and I squared, not by funnel plot shape, and the pooled effect size itself is read from the diamond, not the scatter pattern.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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