How to design efficient cluster randomised trials

How to design efficient cluster randomised trials

Cluster randomised trials have diminishing returns in power and precision as cluster size increases. Making the cluster a lot larger while keeping the number of clusters fixed might yield only a very small increase in power and precision, owing to the intracluster correlation. Identifying the point at which observations start making a negligible contribution to the power or precision of the stu...

Cluster randomised trials.

Although randomised controlled trials are the reference methodology to assess the effects of therapeutic interventions, for interventions that naturally occur in groups of individuals random allocation of participants may be inappropriate. In these cases, the unit of random allocation may be the group or cluster, rather than the individual. Clinical trials that randomly allocate groups or clust...

CONSORT statement: extension to cluster randomised trials.

Changing cluster composition in cluster randomised controlled trials: design and analysis considerations

BACKGROUND There are many methodological challenges in the conduct and analysis of cluster randomised controlled trials, but one that has received little attention is that of post-randomisation changes to cluster composition. To illustrate this, we focus on the issue of cluster merging, considering the impact on the design, analysis and interpretation of trial outcomes. METHODS We explored th...

Cluster randomised trials : Methodological and ethical considerations