Calculates the 6 intra-class correlations for the columns in the matrix or data.frame x, where the columns are typically raters or items, following Shrout and Fleiss (1979).
Usage
get.ICC(x)
Arguments
x
A matrix or data.frame on which to calculate ICCs of the columns.
Value
A matrix containing the values for the six possible intra-class correlations described by Shrout and Fleiss (1979).
Details
This function is the workhorse function for item.ICC and Profile.ICC. It computes the intra-class correlations for a single item and for the composite of the items in the data.frame or matrix x. Of note, the results should be intepreted with extreme caution if values in x are missing. If possible, the best choice is to remove missing values from x first.
References
Shrout, P. E. & Fleiss, J. L. (1979). Intraclass correlations: Uses in assessing rater reliability. Psychological Bulletin, 86, 420-428