The impact of varying cluster size in cross-sectional stepped-wedge cluster randomised trials.

ABSTRACT:

Background

Cluster randomised trials with unequal sized clusters often have lower precision than with clusters of equal size. To allow for this, sample sizes are inflated by a modified version of the design effect for clustering. These inflation factors are valid under the assumption that randomisation is stratified by cluster size. We investigate the impact of unequal cluster size when that constraint is relaxed, with particular focus on the stepped-wedge cluster randomised trial, where this is more difficult to achieve.

Methods

Assuming a multi-level mixed effect model with exchangeable correlation structure for a cross-sectional design, we use simulation methods to compare the precision for a trial with clusters of unequal size to a trial with clusters of equal size (rela

SUBMITTER: Martin JT 

PROVIDER: S-EPMC6570871 | biostudies-literature | 2019 Jun

REPOSITORIES: biostudies-literature