I followed the longitudinal example provided in the wiki (http://surfer.nmr.mgh.harvard.edu/fswiki/LinearMixedEffectsModels#a.29Univariate), with the ADNI example. But I am not sure what to use for the "common random effect design matrix" Zi and "column" ZiCol with the lme_plannedSampleSize(Zi,ZiCol,Dhat,phisqhat,effsz,dr,pw,alpha,gr_pr) function:

Here is what I do in matlab:

> load('ADNI791_Hipp_and_Entorh.mat')

> total_hipp_vol_stats = lme_fit_EM(X_Hipp,[1,2],Y(:,1)+Y(:,2),ni);

> lme_plannedSampleSize(total_hipp_vol_stats.X,[1,2],total_hipp_vol_stats.Dhat,total_hipp_vol_stats.phisqhat,1,.2,.8,0.05)

> ans =

   1.0e+07 *

    1.3584    0.0154

    0.0154    0.0100

Is that right?

Regards,

Nicolas