help iccvar

Title

iccvar -- intraclass correlation values and stadard errors for 2, 3, and 4 level models after xtmixed or mixed.

Syntax

iccvar, [unb]

iccvar has a special routine for 3-level models with unbalanced data. To enact this routine use the unb option.

Description

iccvar is a post-estimation command for xtmixed or mixed. After fitting a 2, 3, or 4 level model with a random intercept
(random slopes are not supported), iccvar will calculate the intraclass correlation (ICC) values and the associated standard
errors based on the variance components and standard errors of the variance components estimated from xtmixed.

Saved results

iccvar saves the following in r():

Scalars

r(p) the harmonic mean number of level 2 units per level 3 unit

r(r) the harmonic mean number of level 3 units per level 4 unit

r(tv) the total estimated variance

r(lkvc) the k level variance component

r(lkvc_v) the k level variance component variance

Macros

r(model) the xtmixed model

Matrices

r(b) the matrix of ICCs

r(V) the variance-covariance matrix of ICCs

Acknowledgments

The algorithms used in this program are based on

Hedges, L. V., E. C. Hedberg and A. M. Kuyper. 2012. The Variance of Intraclass Correlations in Three- and Four-Level Models. Educational and Psychological Measurement. DOI: 10.1177/0013164412445193. Click for paper: link.

Contact

This program was written by Eric Hedberg, National Opinion Research Center at the University of Chicago.
Any questions or comments can be directed to ech@uchicago.edu.