Hi,
If you are just repeating the same condition 7 times in each subject then the Three Level Analysis is fine, but I'm guessing from the contrasts in your design that this is not the case (although you haven't really explained this).
The design you attach is problematic because it is rank deficient (it models the mean value in two different ways) and also cannot model the between-subject and within-subject variances correctly (as the residuals will be a mixture of these variances and the GLM does not know this).
Instead I think you would be better off doing a two level analysis where you calculate a single measure of interest from each subject and then feed this up to the higher level analysis. Given your contrasts, it seems that you have a fairly simple question that could be set up as a contrast for each subject, and then you can easily feed this up to a very straightforward higher-level analysis that just averages across the group.
All the best,
Mark
On 10 Nov 2013, at 02:04, Vincent <[log in to unmask]> wrote:
> Dear FSL experts,
>
>
> I am trying to figure out the best way to create a model for a one-group, 7 time points repeated measures ANOVA.
>
>
> The FSL GLM wiki states that: "FEAT has the ability to accommodate independent data with heterogeneous variance (the mixture of common between subject variance and subject-varying measurement error noise), but cannot account for arbitrary repeated measures correlation. Likewise, randomise cannot accommodate general repeated measures designs. That said, there are several very special cases where the GLM (and Feat, and randomise) can model repeated measures, though usually with assumptions and caveats."
>
>
> The "Multi-Session & Multi-Subject (Repeated Measures - Three Level Analysis)" (http://fsl.fmrib.ox.ac.uk/fsl/fslwiki/GLM#Multi-Session_.26_Multi-Subject_.28Repeated_Measures_-_Three_Level_Analysis.29) however, seems eligible as a model. Is this the only right model for a one-group, 7 time points, within subjects repeated measures ANOVA, if I want to use FSL randomise?
>
> Why can I not just use 'this' (see attachment) design?
>
> Thanks,
>
> - Vincent
> <Model.png>
|