Objective
To summarise intra-cluster correlation coefficient (ICC) estimates for pupil health outcomes from
school-based cluster randomised trials (CRTs) across world regions and describe their relationship with
study design characteristics and context.
Study Design and Setting
School-based CRTs reporting ICCs for pupil health ...
Objective
To summarise intra-cluster correlation coefficient (ICC) estimates for pupil health outcomes from
school-based cluster randomised trials (CRTs) across world regions and describe their relationship with
study design characteristics and context.
Study Design and Setting
School-based CRTs reporting ICCs for pupil health outcomes were identified through a literature search
of MEDLINE (via Ovid). ICC estimates were summarised both overall and for different categories of
study characteristics.
Results
Two hundred and forty-six articles reporting ICC estimates were identified. The median (interquartile
range) ICC was 0.031 (0.011 to 0.08) at the school level (N=210) and 0.063 (0.024 to 0.1) at the class
level (N=46). The distribution of ICCs at the school level was well described by the beta and exponential
distributions. Besides larger ICCs in definitive trials than feasibility studies, there were no clear
associations between study characteristics and ICC estimates.
Conclusion
The distribution of school-level ICCs worldwide was similar to previous summaries from studies in the
United States. The description of the distribution of ICCs will help to inform sample size calculations
and assess their sensitivity when designing future school-based CRTs of health interventions
