A cluster randomised trial is a type of experimental study design in which groups, or clusters, of participants are randomly assigned to different treatment or intervention groups, rather than individual participants. The clusters could be naturally occurring groups, such as schools, hospitals, communities, or clinics. This design is often used when it’s not feasible or practical to randomise individuals, or when the intervention is intended for a group rather than individuals.
Cluster randomised trials have been used in trauma medicine multi-centre clinical trials assessing the effectiveness of pre-hospital administration of blood products air ambulance services rather than patients are randomised.