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Hello David,
    EV1 is modelling the difference between A and B. The calculated Beta value is not what might be expected though. As contrasts of this type can be tricky - it’s easier to understand the general concept by considering a “toy” example:

If Y=
4
8
21

and X= 
1 1 1
-1 0 1
0 -1 1

Then you can simply solve Y=XB for the Betas (B) and see how the calculated values relate to the “known” values of A-B etc. 

Hope this helps,
Kind Regards
Matthew

--------------------------------
Dr Matthew Webster
FMRIB Centre 
John Radcliffe Hospital
University of Oxford

On 20 Jun 2018, at 17:48, David Hofmann <[log in to unmask]> wrote:

Thank you Anderson!

I'm afraid it is not entirely clear to me how you modeled this. I may be reading this entirely wrong, but as far as I understand EV1 models the difference between A and B, EV2 models A-C and EV3 A-D asf. for the other group. And EV7 to EV14 account for the between-subjects effects.

Now, I'm not sure how the contrasts come about. Taking for example, C1, which should model the linear combination of the EV1 to EV6, i.e.: 2*EV1+1*EV2+1*EV3+2*EV4+1*EV5+1*EV6. How does this linear model A>B?

Also, what would be the 2-way interaction contrast?

Thanks for the support!

David



2018-06-20 10:05 GMT+02:00 Anderson M. Winkler <[log in to unmask]>:
Hi David,

I believe this question has appeared before. Please see this design: https://s3-us-west-2.amazonaws.com/andersonwinkler/mailinglist/design_tim2.ods.


The A, B, C and D would be the 2x2 within subject conditions, and the two groups are then the between-subject final "x2" of your 2x2x2.

All the best,

Anderson


On 13 June 2018 at 19:02, David Hofmann <[log in to unmask]> wrote:
Hi all,

I'm trying to run a 2x2x2 ANOVA with one between-subject factor (Controls, patients) and two within-subject factors with 2 levels (pos. feedback/neg. feedback and observation/no observation). The number of subjects in each group is different. 

I want to calculate the 3 main effects (group, feedback, observation) as well as the 2-way (group x feedback) and 3-way interactions (group x feedback x observation). However, I'm not sure how to create a design matrix for this. 

Any help appreciated!

greetings

David




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