Appropriate statistical methods were infrequently used in cluster-randomized crossover trials

Statistical models appropriate for designs often used in group-randomized trials.

Group-randomized trials are characterised by the allocation of identifiable groups rather than individuals to study conditions; members within those groups are then observed to assess the effect of the intervention. It is convenient to categorize the designs employed in group-randomized trials along two dimensions, each with two levels. The first distinguishes between designs having just one or...

Developing Appropriate Methods for Cost-Effectiveness Analysis of Cluster Randomized Trials

AIM Cost-effectiveness analyses (CEAs) may use data from cluster randomized trials (CRTs), where the unit of randomization is the cluster, not the individual. However, most studies use analytical methods that ignore clustering. This article compares alternative statistical methods for accommodating clustering in CEAs of CRTs. METHODS Our simulation study compared the performance of statistica...

Statistical methods for analyzing sequentially randomized trials.

In this issue of the Journal, Thall et al. present the results of a clinical trial that makes use of sequential randomization, a novel trial design that allows the investigator to study adaptive treatment strategies. Our aim is to complement this groundbreaking work by reviewing the current state of the art of statistical methods available for such analyses. Using the data collected by Thall et...

Methods for sample size determination in cluster randomized trials

BACKGROUND The use of cluster randomized trials (CRTs) is increasing, along with the variety in their design and analysis. The simplest approach for their sample size calculation is to calculate the sample size assuming individual randomization and inflate this by a design effect to account for randomization by cluster. The assumptions of a simple design effect may not always be met; alternativ...

Cluster Unit Randomized Trials