A meta-analysis reports a pooled odds ratio of 2.1 (95% CI: 1.8–2.5, I² = 72%). Which statement BEST describes the interpretation of the I² value?
- A 72% of the variability across studies is due to true heterogeneity beyond chance ✓
- B 72% of the total variability is due to sampling error
- C The pooled OR is unreliable because I² exceeds 50%
- D 72% of studies show a statistically significant result
Correct answer: A. 72% of the variability across studies is due to true heterogeneity beyond chance
Explanation
I² quantifies the proportion of total variation across studies attributable to genuine heterogeneity rather than chance. An I² of 72% indicates substantial heterogeneity. It does not invalidate the pooled estimate but signals that a random-effects model is appropriate and subgroup analyses should be considered. Options A, C, and D misinterpret the statistic.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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