Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 2 of 2
Full-Text Articles in Medicine and Health Sciences
The Small Sample Inferences Of Cluster-Randomized Trials, Peng Li
The Small Sample Inferences Of Cluster-Randomized Trials, Peng Li
All ETDs from UAB
Generalized estimating equation (GEE) and generalized linear mixed model (GLMM) are two statistical modeling methods commonly used in the analyses of correlated outcomes from cluster-randomized trials (CRTs). The fact that most CRTs involve only a small number of clusters makes the small sample adjustment critical to preserve the type I error rates in testing the null hypothesis of intervention effects. To improve the small sample performance of GEE, some bias-corrected sandwich estimators have been proposed. To improve the small sample performance of GLMM, the approximated Wald F test is used to replace the asymptotic ÷^2 test and the denominator degrees …
Power Issues And Internal Pilot Designs For Cluster-Randomized Trials With Unequal Cluster Sizes, Ashutosh Ranjan
Power Issues And Internal Pilot Designs For Cluster-Randomized Trials With Unequal Cluster Sizes, Ashutosh Ranjan
All ETDs from UAB
Cluster-randomized trials that randomize groups of individuals, instead of individuals themselves, run the risk of being underpowered when they are designed assuming equal cluster sizes but end up recruiting unequal clusters. The loss in power of the trial is directly related to the amount of variation present among the cluster sizes. To overcome the loss in power, researchers often employ a weighted analysis of the cluster means. Different weighting procedures have been developed that appear to maintain the power of the trial but there have been fewer attempts to describe the impact of different weights on the type I error …