ICC {psych}R Documentation

Intraclass Correlations (ICC1, ICC2, ICC3 from Shrout and Fleiss)

Description

The Intraclass correlation is used as a measure of association when studying the reliability of raters. Shrout and Fleiss (1979) outline 6 different estimates, that depend upon the particular experimental design. All are implemented.

Usage

ICC(x,digits=2)

Arguments

x a matrix or dataframe of ratings
digits Round the output to digits

Details

Shrout and Fleiss (1979) consider six cases of reliability of ratings done by k raters on n targets.

1) Each target is rated by a different set of k judges. 2) A random sample of k judges rate each target 3) A fixed set of k judges rate each target. Then, for each of these cases, is reliability to be estimated for a single rating or for the average of k ratings? (The 1 rating case is equivalent to the average intercorrelation, the k rating case to the Spearman Brown adjusted reliability.

Value

ICC1 Intraclass correlation for different judges
ICC2 Intraclass corelation for the same random judges
ICC3 Intraclass corelation for the same fixed judges
ICC12 Intraclass corelation for the average of different judges
ICC22 Intraclass corelation for the average of random judges
ICC3 Intraclass corelation for the average of fixed judges

Author(s)

William Revelle

References

Shrout, Patrick E. and Fleiss, Joseph L. Intraclass correlations: uses in assessing rater reliability. Psychological Bulletin, 1979, 86, 420-3428.

Revelle, W. (in prep) An introduction to psychometric theory with applications in R. Springer.

Examples

ICC(attitude)

[Package psych version 1.0-58 Index]