This is most easily done using the 'Flexible Factorial'
1. Create two factors.
2. Call the the first one Subject. Independence Yes, Variance Equal.
3. Call the second one 'Condition'. Independence Yes, Variance Unequal.
4. Under, Specify Subjects or all Scans, Choose Subjects
5. Under Subjects, create a new 'Subject' for each subject that you have
6. Then, for each Subject, under 'Scans'. Enter the 4 scans you have for
7. Also, for each Subject, under 'Conditions' enter the vector [1:4]
8. Under Main effects and Interactions create 2 main effects; factor 1
and factor 2.
9. Specify other covariates as necessary and your o/p directory.
10. Then save your design job as 'within_subject_design' and press run.
I have attached my saved job file 'within_subject_design.mat' as a
template for you. When you run it, SPM should create the design matrix
shown in 'design-matrix.png'.
Note the 5 subject columns on the left. Without these 5 columns
you do not have a 'within-subject' design.
Also I have treated your 2 x 2 design as a 1 x 4. So you'll need to bear
this in mind when doing your contrasts eg. 1 1 -1 -1 and 1 -1 1 -1 to
test for main effects and 1 -1 -1 1 for the interaction (of course,
pre-pad these with 5 0's).
Michiru Makuuchi wrote:
> I have tired to perfrom 2 x 2 within-subjects ANOVA in SPM5, but I
> couldn't find
> how I could do that in 'Full factorial' dsign. Therefore I designed the
> design matrix
> via 'Multiple regression' option. The resulted design matrix was similar
> to Fig 7 of
> Henson and Penny's online document (ANOVA and SPM). The difference was
> only the position
> of constant term. In Fig 7, it was the 4th column, but it was on the
> last column in my design matirix.
> Here are my questions.
> Is my approach acceptible for the purpose?
> Can someone point out the exact procedure to build the model for 2 x 2
> within-subject ANOVA?
> Best regards,
> Michiru Makuuchi
> Max Planck Institute
> for Human Cognitive and Brain Sciences
> Stephanstrasse 1a, 04103 Leipzig, Germany
William D. Penny
Wellcome Trust Centre for Neuroimaging
University College London
12 Queen Square
London WC1N 3BG
Tel: 020 7833 7475
FAX: 020 7813 1420
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