Hi Dr. Greve,

Sorry about that - I had followed the "Reply via email" link on the archive page instead of posting to the forum directly. 

Thank you for this response. Can extracting the means be done at the whole-brain level? If we get the means and variances for each group, I'm assuming we would need to use ROIs. Could you please clarify whether it's possible to extract means across the whole brain?

Thank you,
Hannah

Re: [Freesurfer] Welch's t-test for HOV violation
2019-03-13 Thread Greve, Douglas N.,Ph.D.
Hi Hannah, please include the previous correspondence so that we have context. 
Also, please remember to post to the list and not to us personally.
thanks!
doug


On 3/13/19 10:52 PM, Hannah CK wrote:

External Email - Use Caution

Hi Dr. Greve,

Thank you for this response. Can extracting the means be done at the 
whole-brain level? If we get the means and variances for each group, I'm 
assuming we would need to use ROIs. Could you please clarify whether it's 
possible to extract means across the whole brain?

Thank you,
Hannah

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Re: [Freesurfer] Welch's t-test for HOV violation
2019-03-11 Thread Greve, Douglas N.,Ph.D.

I used to have this about 20 years ago, but I stopped supporting it when 
it did not fit cleanly into the GLM ...
The shortest route is probably to do two separate analyses with 
mri_glmfit, one for each group. This will output means and variances for 
each group. Then use fscalc to compute maps of the Welch's t.

On 3/11/19 1:28 PM, Hannah CK wrote:
>
>         External Email - Use Caution
>
> We are conducting t-test comparisons across groups in which there is a 
> large discrepancy in group sizes. HOV is violated. I've searched for 
> ways to run Welch's t-test in FreeSurfer (or a similar analysis that 
> does not assume homogeneity of variance) but am not finding one.
>
> Could anyone please advise on how to do this?
>
> Thank you.