Intraclass correlation coefficients from three cluster randomised controlled trials in primary and residential health care

Abstract

OBJECTIVE: This paper provides intraclass correlation coefficients (ICCs) for estimation of sample size inflation required in future cluster randomised trials in primary or residential care. METHODS: Three cluster randomised trials were conducted among middle-aged and older adults in primary care and residential care in Australia and New Zealand between 1995 and 2002. Baseline means or proportions, mean change, and ICCs with their standard errors and 95% confidence intervals are reported for outcome variables used in the three studies. The ICCs were estimated from a one-way random effects model using the analysis of variance method. RESULTS: ICCs for quality of life and psychological variabl..