On 6/15/14 2:24 PM, wangzhiwei3233 wrote:

Hi, all,

I have two quesiotns about clusterwise correction for multiple comparsion.

I run 2 corrections for one same result,and commands are as follows:

a. mri_glmfit-sim --glmdir g2v0.weight --cache 2.0 abs --cwpvalthresh .05 --2spaces

b. mri_glmfit-sim --glmdir g2v0.weight --cache 2.0 pos --cwpvalthresh .05 --2spaces

The only difference is the sign of voxel-wise results.

Question 1 : Should the postive clusters from "abs" be same as the cluster from "pos"? If yes, why cluster size from "pos" are different from postive cluster from "abs" in my case?(see results)

Resluts form a (only positive clusters are listed):

# ClusterNo Max VtxMax Size(mm^2) MNIX MNIY MNIZ CWP CWPLow CWPHi NVtxs Annot

3 6.483 140982 222.17 -14.8 58.9 -6.1 0.01510 0.01350 0.01670 281 rostralmiddlefrontal

8 5.208 45661 266.48 -6.7 42.3 -22.2 0.00450 0.00370 0.00540 454 medialorbitofrontal

9 5.103 84832 241.36 -32.0 30.7 -2.3 0.00830 0.00710 0.00950 655 lateralorbitofrontal

Resluts form b:

# ClusterNo Max VtxMax Size(mm^2) MNIX MNIY MNIZ CWP CWPLow CWPHi NVtxs Annot

1 6.483 140982 253.31 -14.8 58.9 -6.1 0.02000 0.01820 0.02180 326 rostralmiddlefrontal

2 5.208 45661 402.16 -6.7 42.3 -22.2 0.00080 0.00050 0.00120 727 medialorbitofrontal

3 5.103 84832 287.61 -32.0 30.7 -2.3 0.01010 0.00880 0.01140 772 lateralorbitofrontal

Usually they would be the same, but they don't have to be if negative and positive vertices are right next to eachother to form a larger cluster. I would not have thought this could happen, but check your data.

Question 2 : Is the simulation from pre-cached independent from my results waiting for being corrected?

I'm not sure what you mean. The pre-cached data are "independent" in that they were computed without reference to it (as opposed to FDR or permutation). It is the same for t-tests, F-tests, and all parametric statistics.

Thanks a lot!

Wilder

2014/06/15

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