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Table 2 Reasons for rating randomised trials as high ROB for sequence generation in Cochrane reviews

From: Risk of bias assessment of sequence generation: a study of 100 systematic reviews of trials

Review Number of randomised trials rated as high ROB for sequence generation (% of total included randomised trials) Justification for high ROB for sequence generation (as stated by the review authors)
Lund et al. [13] 3 (75%) Altinli 2007: “Participants were randomised into 2 groups, according to the day the participant was first seen in the clinic (odd and even days).”
Sozen 2011a: “The participants were randomised into 2 groups—drained and fibrin sealant—according to the admission protocol number. Details of this protocol number unclear.”
Sozen 2011b: “The participants were randomised into two groups, drained and non-drained, according to the admission protocol number. Nature of this protocol number unclear.”
Cheng et al. [9] 1 (16.7%) Randomisation may have not been executed properly as there was a large difference in the number of participants in each arm; the acupuncture arm had 25/109 (40%) more participants than the control group. A random number table was used to generate sequence. Odd numbers were allocated to treatment group, even numbers were allocated to control group.
Chauhan et al. [14] 1 (2.7%) Participants were randomised to 2 groups according to their order of presentation at the outpatient clinic.
McCaughan et al. [15] 1 (16.7%) The randomisation protocol was compromised by selecting patients serially as they registered.
Menting et al. [8] 2 (6.9%) Czibik-stable 2008 and Czibik-unstable 2008: “Randomisation not reported”