[pymvpa] group level test on decoding accuracy

Jingwen Jin jinjingwen111 at gmail.com
Sat May 9 16:49:31 UTC 2015

Hi MVPA experts,

I have a general question about conducting group-level analysis on the
subjects' classification accuracy maps. Let's say I am doing a one-sample
t-test to find the voxels that have high classification accuracy across
subjects. Essentially, I am doing a t-test on percentage numbers (SVM
classification accuracy measured as percentage correct). Since percentage
is highly affected by the testing example numbers, and in general would
probably not meet the normal distribution assumption for t-test.

So my question is if people adjust for testing trial numbers or any sort of
transformation? For example, I converted each voxel's percentage number to
a z score at the individual subject's classification map level, and then do
group-level t-test on these z score maps. I wonder if this is valid?

Thank you very much!

Jingwen Frances Jin
Department of Psychology, PhD candidate in Clinical area
Stony Brook University
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