External Email - Use Caution
Dear Dr. Douglas,
Thank you so much for your quick response! You saved my half life.
From the introduction of clusterwise correction for multiple comparisons, I
have a few questions.
1, What is the null hypothesis here ?
2, What is a z map? Do you mean synthesize cortical datasets?
3. Smooth z map, what FWHM do you use, if it is not consistent with my
FWHM, how will it affect the results?
4, Threshold z map, what does level mean? Does it mean the vertex p-value?
Clusterwise Correction for Multiple Comparisons
To perform a cluster-wise correction for multiple comparisons, we will run
a simulation. The simulation is a way to get a measure of the distribution
of the maximum cluster size under the *null **hypothesis*. This is done by
iterating over the following steps:
1. Synthesize a z map
2. Smooth z map (using residual FWHM)
3. Threshold z map (level and sign)
4. Find clusters in thresholded map
5. Record area of maximum cluster
6. Repeat over desired number of iterations (usually > 5000)
Thank you so much!
Best regards,
Ting
On Mon, Dec 2, 2019 at 10:20 AM Greve, Douglas N.,Ph.D. <
dgr...@mgh.harvard.edu> wrote:
> That will use the pre-computed ("cached") CSD files distributed with
> FreeSurfer. This used 10,000 iterations.
>
> On 12/1/2019 11:34 PM, Ting Li wrote:
>
> External Email - Use Caution
> Dear Freesurfer Expert:
>
> I have used the simulation code as show below:
>
> mri_glmfit-sim \
> --glmdir lh.gender_age.glmdir \
> --cache 4 neg \
> --cwp 0.05\
> --2spaces
>
> My question is how many iterations are done during this simulation? I
> didn’t specify the iteration number.
>
> Why I didn’t have the csd file?
>
> Thanks a lot for your response!
>
> Best regards,
> Ting
>
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