Cluster correction for the group-level stat after multivariate analysis

Dear AFNI experts,

I have a question how to go about FWE cluster-wise correction after a mild smoothing applied only for the group analysis.

I ran a multivoxel pattern analysis on a native space (without any spatial smoothing), but I wanted to apply a very mild smoothing just prior to the group analysis (i.e., smoothing right after spatial normalization step).
So in this case, I would like to know how I should run 3dClustSim. I read that -acf option takes residual time series (in the standard space), and in my case I only want the smoothing for the group-level… Should I regenerate residual time series in non-smoothed native space data, and run 3dFWHMx to get parameters for acf?

Also, I make use of 3dLME because of some covariates with multiple factors (but also sometimes 3dttest++).

Thanks for your help,

Best, Michelle.


If you have the most recent version of AFNI, there is an option -resid in 3dLME that allows you to output the residuals at the group level. Then you can use 3dFWHMx to estimate the ACF values based on the group residuals.

Dear Gang,

Thank you very much for your input. I have been using afni version from this year January, 2016. I am trying to run with the new version. I hope the update does not affect too much of the prior analyses that I did.