Cluster randomised controlled trial

Cluster randomised controlled trial

A cluster randomised controlled trial is a type of randomised controlled trial in which groups of subjects (as opposed to individual subjects) are randomised.[1] Cluster randomised controlled trials are also known as cluster randomised trials[2], group-randomised trials[3][4], and place-randomized trials[5].

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 the ability to study interventions that cannot be directed toward selected individuals (e.g., a radio show about lifestyle changes) and the ability to control for "contamination" across individuals (e.g., one individual's changing behaviors may influence another individual to do so).[6] 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]


  1. ^ a b Bland JM (2004). "Cluster randomised trials in the medical literature: two bibliometric surveys". BMC Med Res Methodol 4: 21. doi:10.1186/1471-2288-4-21. PMID 15310402. 
  2. ^ a b Campbell MK, Elbourne DR, Altman DG; CONSORT group (2004). "CONSORT statement: extension to cluster randomised trials". BMJ 328 (7441): 702–8. doi:10.1136/bmj.328.7441.702. PMID 15031246. 
  3. ^ Murray DM, Varnell SP, Blitstein JL (2004). "Design and analysis of group-randomized trials: a review of recent methodological developments". Am J Public Health 94 (3): 423–32. doi:10.2105/AJPH.94.3.423. PMID 14998806. 
  4. ^ Patton GC, Bond L, Carlin JB, Thomas L, Butler H, Glover S, Catalano R, Bowes G (2006). "Promoting social inclusion in schools: a group-randomized trial of effects on student health risk behavior and well-being". Am J Public Health 96 (9): 1582–7. doi:10.2105/AJPH.2004.047399. PMID 16873760. 
  5. ^ Boruch R, May H, Turner H, Lavenberg J, Petrosino A, De Moya D, Grimshaw J, Foley E (2004). "Estimating the effects of interventions that are deployed in many places: place-randomized trials". Am Behav Sci 47 (5): 608–633. doi:10.1177/0002764203259291. 
  6. ^ Edwards SJ, Braunholtz DA, Lilford RJ, Stevens AJ (1999). "Ethical issues in the design and conduct of cluster randomised controlled trials". BMJ 318 (7195): 1407–9. PMID 10334756. 

Further reading

  • Murray DM. Design and analysis of group-randomized trials. New York: Oxford University Press, 1998. ISBN 0195120361
  • Mosteller F, Boruch RF. Evidence matters: randomized trials in education research. Washington, DC: Brookings Institution Press, 2002. ISBN 0815702043
  • Boruch RF. Place randomized trials: experimental tests of public policy. Thousand Oaks, CA: Sage Publications, 2005. ISBN 1412925827