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Table 1 Distribution of Cochrane reviews over inclusion criteria

From: Are more observational studies being included in Cochrane Reviews?

Study design inclusion criteria Total of which published:
pre-2008 2008-2009
Number (per cent) Number (per cent) Number (per cent)
(A1) Randomised controlled trials 3,398 (87.2) 2,563 (87.9) 835 (85.2)
(A2) Randomised controlled trials and quasi-randomised trials 277 (7.1) 199 (6.8) 78 (8.0)
(B) Randomised controlled trials, quasi-randomised trials, and (some subset of) observational studies 222 (5.7) 155 (5.3) 67 (6.8)
Total 3,897 (100.0) 2,917 (100.0) 980 (100.0)
  1. Source: Cochrane Database of Systematic Reviews, Issue 3, 2009. A list of the categories assigned to individual reviews is found in the Additional file 1.