Dear experts,
I have volume data for a number of subjects and timepoints, and I would like to test if there is any group difference between different timepoints. The problem is that the data have rather different scales.
For example;
Subject 1, timepoint 1, the scale is [-500, 1200]
Subject 1, timepoint 1, the scale is [-600, 1500]
Subject 1, timepoint 1, the scale is [-400, 1800]
Subject 1, timepoint 1, the scale is [-700, 1100]
This makes it a bit hard to know if the change in value in a specific voxel is due to a real change or due to a scale change. What do you think is the best preprocessing option before I do a t-test with randomise?
1) Do nothing.
2) Normalize the values to be within the scale [0,1].
3) Normalize each volume to have a L1-norm of 1.
4) Normalize each volume to have a L2-norm of 1.
5) Other?
cheers,
Anders
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