Hello Silke,
a multiple regression model would mdel this best, yes, so the psychometric
measure would represent one regressor, and TIV the other one. Further
typical covariates as age and gender can be added if needed.
The contrast to interrogate would be +1 or -1 set onto your psychometric
variable (whereever that is positioned).
(If it is positioned as first regressor, you can leave away any zeros as
these are automatically appended by SPM)
best regards,
Philipp
Max Planck Institute of Psychiatry
NMR Research Group
Kraepelinstr. 2-10
80804 Munich
Mail: [log in to unmask]
Phone: 0049-89-30622-413
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