I have a question about how to calculate an intraclass correlation coefficient in a mixed model that has both a random intercept and a random slope. I have a very nice paper by Judith Singer that describes how to do this for a random intercept model. The paper can be accessed at:

http://www.gse.harvard.edu/~faculty/singer/Papers/Using Proc Mixed.pdf

At the top of page 330, there is a formula for calculating the ICC for a random intercept model. There's also a section on individual growth models, that starts on page 340. The growth models have a random intercept and a random slope. Is there some way to extend the formula on page 330, so I can calculate the ICC for growth models like that described on pages 340 and 341? If so, how is this done?

Thanks,

Paul