Background: Many investigators rely on previously published point estimates of the
intraclass correlation coefficient rather than on their associated confidence intervals to …

A Correction has been published for this article in Statistics in Medicine 23 (18) 2004, 2935.
This study compared different methods for assigning confidence intervals to the analysis of …

Sample size calculations for cluster-randomised trials require inclusion of an inflation factor
taking into account the intra-cluster correlation coefficient. Often, estimates of the intra …

Background The first applications of cluster randomized trials with three instead of two levels
are beginning to appear in health research, for instance, in trials where different strategies to …

Objectives: Cluster randomised trials, in which groups of individuals are randomised, are
increasingly being used in the health field. Adopting a clustered approach has implications …

OBJECTIVE: Simple guidelines for calculating efficient sample sizes in cluster randomized
trials with unknown intraclass correlation (ICC) and varying cluster sizes. METHODS: A …

Background Cluster randomization trials are widely used to test the effect of an intervention
when individuals are naturally found in groups such as communities. For several separate …

The intraclass correlation coefficient ρplays a key role in the design of cluster randomized
trials. Estimates of ρ obtained from previous cluster trials and used to inform sample size …

Background Increasingly, researchers are recognizing that there are many situations where
the use of a cluster randomized trial may be more appropriate than an individually …

The intra‐cluster correlation coefficient (ICC) of the primary outcome plays a key role in the
design and analysis of cluster randomized trials (CRTs), but the precise definition of this …