> Yes, if you could add that option it would be great. Why would one consider session effect as random and not fixed?

I've modified the program so that the user can specify the fixed effects. And a variable can be modeled with either fixed or random effects, or both.

Currently the fixed effects are not provided in the output.

The modifications will be available in the next AFNI build. If you want it earlier, send me an email.

Regarding ICC for consistency and absolute agreement: they seem to be defined in the conventional ANOVA framework. I'm not so sure whether they have their counterpart in the context of linear mixed-effects model.

> we want to generate separate ICC maps for two tasks. We want to compare
> ICC values from both tasks to see if they are significantly different from each other.

Other than comparing them quantitatively, I don't have any idea about significance testing. Never saw anything like in the literature under the LME framework.

> I'm still confused. Aren't we interested in reliability though? So, if we are looking for
> reliability, wouldn't that suggest we'd be interested in low ICC values? Is this correct?
> I was under the impression that high ICC values indicate strength of reliability, reproducibility, no?

My understanding about the notion of reliability/reproducibility is this: the ICC for session is also the correlation coefficient between any two measures (from two different subjects, for example) coming from the same session. And it has nothing to do with the difference between the two sessions, which is measured by the fixed effect.

Gang



Edited 1 time(s). Last edit at 07/31/2013 12:10PM by Gang.