Table 1.

Summary results of 95% confidence intervals (CIs) and 95% prediction intervals (PIs) among the 65,931 Cochrane meta-analyses.

Scenario	No. of meta-analyses (%)
Interval covering the null value or not
95% CI not covering the null	18,549 (28.1%)
95% CI covering the null	47,382 (71.9%)
95% PI not covering the null	10,097 (15.3%)
95% PI covering the null	55,834 (84.7%)
Future studies with true effects potentially in opposite directions to meta-results
95% CI not covering the null but 95% PI covering the null	8,452 (12.8%)
Ratio of PI length over CI length
1.0 (i.e., PI is identical to CI with no heterogeneity)	22,862 (34.7%)
1.0–1.2	14,938 (22.7%)
1.2–1.4	3,537 (5.4%)
1.4–1.6	2,882 (4.4%)
1.6–1.8	2,405 (3.6%)
1.8–2.0	2,037 (3.1%)
2.0–2.2	1,714 (2.6%)
2.2–2.4	1,514 (2.3%)
2.4–2.6	1,418 (2.2%)
2.6–2.8	1,137 (1.7%)
2.8–3.0	1,003 (1.5%)
>3.0	10,484 (15.9%)