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Table 1 Comparison of Cochrane overviews and non-Cochrane overviews

From: Quality ratings of reviews in overviews: a comparison of reviews with and without dual (co-)authorship

  Cochrane overviews (n = 20) Non-Cochrane overviews (n = 78) Mann-Whitney U test (p value) Odds ratio (95% CI)
Included SRs (median, IQR) 10 (6; 18.5) 14 (8.25; 24) 0.184  
SRs affected by DCA per overview (median, IQR) 5 (2.5; 7) 1 (0; 2) <  0.001  
Overviews affected by DCA 18 (90%) 40 (51%)*   8.6 (1.9–39.4)
Independent assessment 8 (44%) 8 (20%)   3.2 (1.0–10.7)
SRs not assessed independently (median, IQR) 0 (0; 4.25) 1 (0; 2) 0.787  
Reported as limitation 5 (28%) 2 (5%)   7.3 (1.3–42.3)
Reported as declaration of interest 11 (61%) 4 (10%)   11.0 (2.8–42.8)
Safeguard 7 (39%) 2 (5%)   12.1 (2.2–66.8)
  1. CI confidence interval, SRs systematic reviews, IQR interquartile range, DCA dual (co-)authorship
  2. *Two overviews were assessed as partly and are not included in the denominator