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) |