A meta-analysis reports an I² statistic of 78%. What does this indicate?
- A 78% of the total variation across studies is due to true heterogeneity ✓
- B 78% of the variation is due to sampling error
- C 78% of studies show a statistically significant result
- D The meta-analysis included 78% of all eligible studies
Correct answer: A. 78% of the total variation across studies is due to true heterogeneity
Explanation
I² (I-squared) quantifies the proportion of total variability in effect estimates across studies that is attributable to true between-study heterogeneity rather than chance. An I² of 78% indicates substantial heterogeneity (>75% is considered considerable per Cochrane guidelines), suggesting that pooling the studies may be inappropriate without exploring sources of heterogeneity.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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