title: Cluster randomization: a trap for the unwary.
abstract: Controlled trials that randomize by practice can provide robust evidence to inform patient care. However, compared with randomizing by each individual patient, this approach may have substantial implications for sample size calculations and the interpretation of results. An increased awareness of these effects will improve the quality of research based on randomization by practice.
authors.affiliation: Department of General Practice and Primary Care, Queen Mary and Westfield College, London.
authors.forename: M
authors.initials: M
authors.lastname: Underwood
authors.forename: A
authors.initials: A
authors.lastname: Barnett
authors.forename: S
authors.initials: S
authors.lastname: Hajioff
mesh_terms: D016000:Cluster Analysis; D016032:Randomized Controlled Trials as Topic