In a meta-analysis, the I² statistic is reported as 78%. The most appropriate interpretation is:
- A 78% of the total variation is due to chance
- B The study should be rejected for pooling
- C High heterogeneity; a random-effects model is more appropriate ✓
- D Low heterogeneity; fixed-effects model is preferred
Correct answer: C. High heterogeneity; a random-effects model is more appropriate
Explanation
I² measures the proportion of total variability across studies due to heterogeneity (true differences between studies) rather than chance. An I² of ≥75% indicates high heterogeneity; 50–75% is moderate; 25–50% is low; <25% is minimal. With I² of 78%, a random-effects model is preferred over fixed-effects, as it accounts for variability between study populations. The study should not be automatically rejected but interpreted with caution.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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