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Table 1 Number of risk of bias tools listed by study designs included

From: Risk of bias tools in systematic reviews of health interventions: an analysis of PROSPERO-registered protocols

Number of tools listed

Study designs to be included in systematic review

N (%)

RCT only

N = 175

RCT and NRS

N = 296

All protocols

N = 471

0

15 (8.6)

31 (10.4)

46 (9.8)

1

156 (89.1)

163 (55.1)

319 (67.7)

2

4 (2.3)

77 (26.0)

81 (17.2)

3+

0 (0.0)

9 (3.0)

9 (1.9)

Suite of tools*

0 (0.0)

16 (5.4)

16 (3.4)

  1. NRS = non-randomized study, RCT = randomized controlled trial
  2. Included quasi-RCT
  3. Included non-randomized experimental designs, quasi-experimental studies, and observational studies
  4. *Suite of tools: the RoB tool was comprised of separate checklists for different study designs produced by the same organization, but the number of checklists to be used was not specified