Hi Mike,
I did not see any figure attached to any of your posts, but I hope I
can imagine what it would look like. In SPM5, you have to tell
explicitly what kind of main effect/interaction columns should appear
in a flexible factorial design matrix (which is more likely what you
want). The dfs being the same in SPM2 and SPM5 is probably due to the
fact, that your block effect columns are linear combinations
of other columns in your design matrix and therefore do not increase
the rank of it.
Volkmar
Quoting Mike Glabus <[log in to unmask]>:
> Firstly, I confess to a little ignorance for the rationale for modeling
> the block effect but assume this is equivalent to the "DC" or offset in
> the GLM, i.e. the y intercept (?).
>
> With that in mind, I have been attempting to replicate an SPM2 design in
> SPM5 for a two-group VBM analysis.
>
> In SPM2 I used the "compare populations 1-scan per subject" with ANCOVA.
> In SPM5 I have tried using both "independent t-test" and "full factorial"
> models, but in both cases, there is no modeled block effect. However, the
> df in both SPM2 and SPM5 designs is the same! (see attached)
>
> Is there an explantation for i) the absence of a modeleed block effect in
> SPM5; ii) the df being the same in SPM2 and SPM5 designs, where one
> (putatively) should have one df less (SPM2).
>
> Regards - MFG
>
>
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