Benjamin Littenberg|Charles D. MacLean
Intra-cluster correlation coefficients in adults with diabetes in primary care practices: the Vermont Diabetes Information System field survey
University of Vermont|University of Vermont
abstract background proper estimation sample size requirements clusterbased studies requires estimates intracluster correlation coefficient icc variables interest methods calculated icc 112 variables measured part vermont diabetes information system clusterrandomized study adults diabetes 73 primary care practices clusters vermont surrounding areas results iccs varied widely around median value 00185 interquartile range 0006 0037 characteristics proportion recent creatinine measurement highly associated practice icc 0288 others prevalence comorbidities complications certain aspects quality life varied much across patients small correlation within practices icclt0001 conclusion icc values reported may useful designing future studies use clustered sampling primary care practices