Dear SPM users,
I am confused about the effect of linear transformation on my results:
We have an event related design with three different (repeated) conditions.
We also have a numeric value for every stimulus and want to determine the
correlation between the bold response and the numeric value. We have
modelled a user defined regressor for each subject in which we used a
boxcar-function with the length of the event and with the numeric value of
the stimulus as the height of the rectangle. This regressor was convolved
with the hrf.
My question is: If I transform the numeric value of every stimulus with the
identical linear function (e.g. original value+10), the results change. This
is confusing. As far as I know correlations are independent under linear
transformations.
Any help would be greatly appreciated!
Patrick
Dipl.-Psych. Patrick Britz
Universität Trier
Fachbereich I
Universitätsring 15
54286 Trier
0651-201-2896
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