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The design and use of cluster randomised controlled trials in evaluating injury prevention interventions: part 2. Design effect, sample size calculations and methods for analysis
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Funding CD was funded in part by a grant from the National Center for Injury Prevention and Control, Centers for Disease Control and Prevention, Atlanta, GA.
Competing interests None.
Provenance and peer review Commissioned; externally peer reviewed.
↵i ICC=σb2/(σb2+σw2) where σb2 is the between-cluster component of variance and σw2 is the within-cluster component of variance.
↵ii An extension of the CONSORT guidelines for the reporting of individually randomised controlled trials, which addresses the unique aspects of reporting CRCTs, has been published.15 At the end of each section, we provide guidelines and examples for reporting the issue discussed, based on the extended CONSORT guidelines.