A systematic review pools results from 8 studies evaluating a dietary intervention. The I² statistic is 72%. Which interpretation is MOST appropriate?
- A The intervention is effective in 72% of studies
- B 72% of the total variance is attributable to between-study heterogeneity ✓
- C 72% of the pooled effect estimate is due to chance
- D The studies are homogeneous and can be combined without restriction
Correct answer: B. 72% of the total variance is attributable to between-study heterogeneity
Explanation
The I² statistic quantifies the proportion of total variation across studies that is due to true between-study heterogeneity rather than sampling error (chance). An I² of ≥75% is considered substantial heterogeneity; 72% suggests considerable heterogeneity, which should prompt exploration of sources (subgroup analysis, meta-regression) and caution in pooling. It does not indicate the proportion of studies showing effectiveness, nor does it reflect within-study variance.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.