Ajay,

> am performing a seed based resting state correlation analysis using age, gender, group and MOCA
> as between group covariates and do no have any within subject covariates.

In that case, you can directly use 3dttest++ instead of 3dMVM by coding all those between-subjects variables as covariates. See the second half of the following page for coding categorical variables in 3dttest++:

[afni.nimh.nih.gov]

> Does the -acf option in 3dClustSim/3dFWHMx address issues raised in this article so that cluster
> extents calculated at p<0.01 are indeed accurate or do you recommend going to a p<0.005/0.001
> in order to address these limitations for limited N (ie 20 per group).

Use the new option -Clustsim in 3dttest++, and it should properly handle FWE correction. Make sure that you have the most recent version of AFNI.

Gang



Edited 1 time(s). Last edit at 07/26/2016 10:59AM by Gang.