Methodological bias in cluster randomised trials

Methodological bias in cluster randomised trials

BACKGROUND Cluster randomised trials can be susceptible to a range of methodological problems. These problems are not commonly recognised by many researchers. In this paper we discuss the issues that can lead to bias in cluster trials. METHODS We used a sample of cluster randomised trials from a recent review and from a systematic review of hip protectors. We compared the mean age of particip...

Cluster randomised trials : Methodological and ethical considerations

Preventing Bias in Cluster Randomised Trials

In randomised trials, internal validity is defined as ‘‘the extent to which the design and conduct of a study are likely to have prevented bias’’ [1,2]. In conducting such trials, trialists try to prevent selection bias through randomisation and allocation concealment (defined as ‘‘the process used to ensure that the person deciding to enter a participant into a randomised controlled trial does...

Bias in randomised factorial trials.

Factorial trials are an efficient method of assessing multiple treatments in a single trial, saving both time and resources. However, they rely on the assumption of no interaction between treatment arms. Ignoring the possibility of an interaction in the analysis can lead to bias and potentially misleading conclusions. Therefore, it is often recommended that the size of the interaction be assess...

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...