Dear SPMers,
We have a FDG study with two groups ( athletes and controls ) and three
levels of exertion. The exertion levels are measured at each person, so this
is a repeated measures experiment. We want to find out the differences
between the
groups and the exertion levels.
We succeeded to test the group differences within exertion levels and the
effects of exertion levels.
Our problem is that we can't test the overall group effect properly.
How to test the group effect with SPM99? What kind of design (model) and
what kind of contrast? We tried in SPM Multi-group : conditions and
covariates. Then we defined the contrast. We tested the 6 first parameters
of the design matrix with
a contrast 1 1 1 -1 -1 -1 , but SPM stated that it is invalid contrast.
Thanks in advance,
Esa Wallius
Turku PET centre, Finland
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|