ICC function

Intraclass correlation

Computes to intraclass correlation for multilevel data (ICC; Snijders & Bosker, 1999, p. 17) for each item and the total scale of a questionnaire (Koopman et al., in press) and the F-test for the null hypothesis that the (total scale) ICC is zero (Snijders & Bosker, 2012, p. 22)

ICC(X)

Arguments

• X: matrix or data frame of numeric data containing a grouping column and the item scores of nrow(X) respondents to ncol(X) - 1 items. Missing values are not allowed

Returns

• itemICC: The ICC per item

• scaleICC: The ICC for the total scale and the corresponding results for the F-test

References

Koopman, L., Zijlstra, B. J. H., & Van der Ark, L. A. (in press). A two-step, test-guided Mokken scale analysis for nonclustered and clustered data. Quality of Life Research. (advanced online publication) tools:::Rd_expr_doi("10.1007/s11136-021-02840-2")

Snijders, T. A. B., & Bosker, R. J. (2012). Multilevel analysis: An introduction to basic and advanced multilevel modeling (2nd ed.). Sage.

Author(s)

Letty Koopman V.E.C.Koopman@uva.nl

L. Andries van der Ark L.A.vanderArk@uva.nl

See Also

SWMDK, MLcoefH,

Examples

# Data example (Koopman et al., 2020)
data(SWMDK)

# Compute ICC
mokken::ICC(SWMDK)