Background
Cluster-randomised trials (CRTs) involve randomising groups of participants (such as hospitals or schools) to different treatment arms.However, there is growing recognition that these different estimators are estimating fundamentally different treatment effects in certain situations.Summary of key concepts.CRTs: cluster-randomised trials; IEEs: independence estimating equations; GEEs: generalised estimating equations; OR: odds ratio.An alternative estimation approach, which is unbiased even in the presence of informative cluster size, is the use of independence estimating equations (IEEs).However, in the absence of informative cluster size, IEEs and cluster-level summaries are likely to be less efficient than mixed-effects models and GEEs with an exchangeable correlation structure due to the working independence assumption.