Get the sign from the gamma.mgh file
On 6/2/2022 12:15 PM, Thalhammer, Melissa wrote:
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Hey guys,
I am working with Freesurfer 7.1.1. to compare two groups' cortical
thickness values within Desikan-Killiany ROIs while correcting for
(mean-centered) sex. I have extracted thickness values within ROIs
into a txt using /aparcstats2table /and have then used /mri_glmfit
--table Study.txt /to perform group analysis on thickness values
within ROIs.
For a future analysis, I want to extract the t-statistic (corrected
for sex) per ROI into a txt/csv. This post (*MailScanner has detected
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states that F.mgh stores the F-ratio, which is F=t^2, so t=sqrt(F).
So, in principle, I should be able to calculate t from my F.mgh file.
However, using the squareroot will only yield positive values. I have
run a t-test on my data (using simply Python scipy.stats.ttest_ind):
the values are actually the same as using sqrt(F), but signs differ
(since t calculated from F can only be positive).
Is there a better way to calculate a t-statistic while regressing out
a covariate within ROIs?
Many thanks in advance, Melissa
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