You can subtract .5 from the volume (fscalc vol.mgh sub .5 -o vol-minus.5.mgh), then do a one-sample group mean (--osgm). You should do a permutation test to correct for multiple comparisons because the residuals definitely won't be Gaussian.
doug


On 10/1/12 9:11 PM, Maryam Vaziri Pashkam wrote:
Its one value per voxel per subject. So there is variane across subjects.  and I want to see weather that value is different from 0.5 instead of 0.

Maryam

On Mon, Oct 1, 2012 at 8:54 PM, Douglas Greve <greve@nmr.mgh.harvard.edu> wrote:

So it is only one volume? This won't work with mri_glmfit. glmfit needs to have a value for each subject so that it can compute the variance across subjects (needed to infer whether a difference from 0 is significant). I don't know of any software that will do it.

doug



On 10/1/12 6:59 PM, Maryam Vaziri Pashkam wrote:
Hi Doug,

The output of the analysis is a volume with performance values in each voxel. the performance ranges between 0 to 1 and I want to see if across subjects there is any region with above chance performance (Chance is 0.5).

Maryam

On Mon, Oct 1, 2012 at 6:10 PM, Douglas N Greve <greve@nmr.mgh.harvard.edu> wrote:
Hi Maryam, I must confess ignorance on search-light analysis. Can  you give me more background on what it is, the output data, and what you want mri_glmfit to tell you?
doug


On 09/30/2012 09:46 PM, Maryam Vaziri Pashkam wrote:
Hi Dough,

 I have run a searchlight analysis on 10 subjects and want to run a random effects analysis with mri_glmfit across subject. I have the results of each subject projected on the fsaverage surface. But I have no idea how to make it to
1) compare the values in each voxel with 0.5 instead of 0
2) how to make it ignore the fact that I dont have variance for each subject and only have a single performance value (support vector machine performance) for each voxel (it looks like the mri_glmfit needs a ces.var.nii)

Any idea how I can do this? Sorry if this is a rookie question. I am totally new to searchlight and random effects analysis in fsfast.

Thanks,
Maryam


--
Douglas N. Greve, Ph.D.
MGH-NMR Center
greve@nmr.mgh.harvard.edu
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