Forming inferences about some intraclass correlation coefficients

Although intraclass correlation coefficients (ICCs) are commonly used in behavioral measurement, psychometrics, and behavioral genetics, procedures available for forming inferences about ICCs are not widely known. Following a review of the distinction between various forms of the ICC, this article presents procedures available for calculating confidence intervals and conducting tests or ICCs developed using data from one-way and two-way random and mixed-effect analysis of variance models.