Hi Michael,

> 1) Having all zeros for visit 1, is this possible? Will that cause any problems?

Try it out, and see if the results make sense.

> 2) Is Compound symmetry the default covariance-variance structure if you don't specify one in the options.

Yes, that's typically the case in 3dLME.

> 3) Is there a way to extract the variance components (residual, between-subject,
> within-subject) from the output of 3dLME. Usually, you can calculate the intraclass
> correlation from those components from linear mixed models.

No, not in the current implementation of 3dLME.

> Is this possible since I do not see an option for covariates for 3dICC_REML?

Currently 3dICC_REML only allows fixed-effects covariates.

> 1) Is there a way to include a time-varying covariate or time-invariant covariate?

You can do that in 3dLME, but not in 3dICC_REML right now.

Gang