A Review of Intraclass Correlation.

Against an historical backdrop, this paper summarizes four uses of intraclass correlation of importance to contemporary researchers in the behavioral sciences. First, it shows how the intraclass correlation coefficient can be used to adjust confidence intervals for statistical significance testing when data are intracorrelated and the independence assumption is violated. Closely related to this discussion is a second application of the intraclass correlation coefficient to research design and sampling methodology in settings in which data are nonindependent. The third example is the use of the intraclass correlation coefficient as a measure of association. Finally, several versions of intraclass correlation coefficients, used as measures of interrater reliability among judges, are described. (Contains 7 tables, 2 figures, and 36 references.) (SLD)