If there is no effect in A vs C, then adding it in the Ftest will make
it weaker than the t-test.
On 02/06/2017 11:54 AM, Leon Ernst wrote:
> Dear Freesurfer experts,
>
> I am comparing cortical thickness data of two patient groups (Group A;
> Group B) and one control group (Group C) without any covariates.
>
> In a simple t-test I observe a significant difference in cortical
> thickness only between Group B and Group C in several clusters
> (corrected p!).
>
> Now I am running an ANOVA ("Three Groups (One Factor/Three Levels), No
> Covariates") as documented in your FSGD examples.
>
> In the output of the f-test (using the following matrix [1 -1 0; 1 0
> -1]) the clusters from my t-test remain but do not survive the
> correction using "mri_glmfit sim" as below.
>
> Do I have to correct the results of my f-test using mri_glmfit-sim? If
> yes, why do I reveal a significant group-difference in the corrected
> t-test and not in the corrected f-test?
>
> mri_glmfit-sim \
> --glmdir lh.gender_age.glmdir \
> --cache 4 neg \
> --cwp 0.05\
> --2spaces
>
> Thank you very much in advance!
>
> Sincerely,
>
> Leon
>
>
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