Dear SPMers,
We're using SPM99 in different PET studies. After we finish the
statistical model estimation, we try to use Matthew's worleyize program
to pool the variance. For some study, this program did reduce the noise
and improve the result. For some study, it just changes the result a
little bit. The program pools the variance through averaging the
Residuals sum-of-squares for all analyzed voxels. So it pooled the
variance across brain of all subjects. The assumption is that the
variance for all subjects' brain remain the same. Is this assumption too
strict? If we use the assumption that the variance for each subject's
brain remain the same, can we use this worsleyize program? Thanks a lot.
Sincerely,
Yanjun
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