Dear Freesurfers,

Sorry for having posted an incorrect question. I basically ran mri_glmfit-sim on both hemispheres and tried both --sim-sign neg and --sim-sign pos. Although I only had 5 iterations, I found no significant clusters on any case. Does that mean that I accept the null hypothesis?

PS: I found in http://www.mail-archive.com/freesurfer@nmr.mgh.harvard.edu/msg23324.html

that 10,000 iterations are commonly used.

Thank you very much!

On Mon, Sep 23, 2013 at 9:47 PM, ye tian <tianye730@gmail.com> wrote:

Dear Freesurfers,

I used the following command line to find significant clusters after glm analysis (before MC clusters attached)

mri_glmfit-sim \
--glmdir lh.meditation_age.glmdir \
--sim mc-z 5 4 mc-z.negative \
--sim-sign neg --cwpvalthresh 0.05\
--overwrite

I didn't find any, i.e., there are no clusters listed in file mc-z.negative.sig.cluster.summary. Does this mean that I should accept the null hypothesis for the whole cortex?

Also, how many iterations of mc do people typically perform? I guess it doesn't make a difference if I do 1000 iterations instead of 5 anyways.

Thank you very much!

Sincerely,
Ye