A cluster-randomised controlled trial is a type of randomised controlled trial in which groups of subjects (as opposed to individual subjects) are randomised.
[6] A 2004 bibliometric study documented an increasing number of publications in the medical literature on cluster-randomised controlled trials since the 1980s.
[1] Advantages of cluster-randomised controlled trials over individually randomised controlled trials include: Disadvantages compared with individually randomised controlled trials include greater complexity in design and analysis, and a requirement for more participants to obtain the same statistical power.
[2] Use of this type of trial also means that the experiences of individuals within the same group are likely similar, leading to correlated results.
Failing to control for intraclass correlation negatively affects both the statistical power and the incidence of Type I errors of an analysis.