Hi - I have a simple question regarding the RFX theory and practice. It
has probably been asked before - sorry. In the original paper and
poster, it looks like the input to the RFX equation is a group of
parameter estimate images (or constrasts of parameter estimate images).
A simple t-test is then carried out on this group of images. However, I
think I am right in saying that in practice SPM uses t images as input
to the RFX equation, and not parameter estimate images. Therefore, is
there a difference because:
a) it doesn't make any difference in practice
OR
b) using t values instead of parameter estimates (i.e., including
scan-scan variance information) is an improvement, as the higher
variance inputs are then de-weighted?
If the latter, would Z values do just as well?
Is using t values theoretically as valid as using parameter estimates?
Thanks very much, Steve Smith, FMRIB
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