Hi, I am new to Freesurfer and the Linear Mixed Effects (LME) Models packages. And I would like to compute sample size from volumetric measures for 2 groups.
I followed the longitudinal example provided in the wiki ( http://surfer.nmr.mgh.harvard.edu/fswiki/LinearMixedEffectsModels#a.29Univar...), 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