 |
 |
On 7/26/07, Steve Smith <[log in to unmask]> wrote: > > Hi Sophie, yes you're probably right that 2x3 isn't quite the same as > 3x2, although presumably the difference really only comes down to > which set of options you want to describe different factors and > levels as fixed or random (see for example the table at the bottom of > http://www.fmrib.ox.ac.uk/fsl/feat5/detail.html#ANOVA3factors2levels ). Hello Steve And thank you for replying to my question. I am sorry however, but I must disagree with you! As I understand it a 2 factor by 3 level design (2x3) is *very* different from a 3 factor by 2 level design (3x2). The former involves 6 unique conditions, the latter 8 (2x2x2). Hence, no simple rearrangement or relabelling from fixed to random can map 6 to 8 dimensions. More particularly, for a FEAT setup, the latter can be modelled by binary classications in the structure of the FEAT design matrix, making it easy to do intra-level comparisons. The former cannot, as it is it necessary to do separate events for each level. > I'm afraid that the number of possibilities for ANOVA designs is > endless so we can't provide examples for all of them! Of course I must sympathise with your positition! But I am so very stuck at the moment as I just cannot get my head around this. I just do not see how to make the design matrix for such a higher order model. I guess from the later post of at least one other person (Kristofer Kinsey) I am not alone! So rather than asking for all possible examples, please please please could you provide ONE example of a higher order ANOVA where there is more than 1 factor (e.g. 2) and these factors are at more than 2 levels (e.g. 3)? I think the simplest example of this is the 2x3 design (and yes I know this is what I originally asked for but feel free to give a better example if it is more helpful)... merci Sophie