Dear Will, Tobias, Yiquan, and Markus,
Thank you for your replies.
However, I am still confused about the implementation of within-subjects
ANOVA in SPM5.
Your design matrix seems to represent one-wayANOVA. I thought that the
design matrix
for two-way ANOVA should 'explicitly' model the main effects and
interaction.
Indeed, the one-way (your design-matrix, or Fig 5 type in 'ANOVAs and
SPM') and
two-way (Fig 7 type) models produced different results for the main
effects and interaction.
Which is more appropriate for the 2 x 2 within-subjects ANOVA?
I would be very grateful for your help.
Best regards,
Michiru
Dr. Michiru Makuuchi
Max Planck Institute
for Human Cognitive and Brain Sciences
Stephanstrasse 1a, 04103 Leipzig, Germany
Will Penny さんは書きました:
> Dear Michiru,
>
> This is most easily done using the 'Flexible Factorial'
> option.
>
> 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
> eg. 5.
>
> 6. Then, for each Subject, under 'Scans'. Enter the 4 scans you have for
> each subject.
>
> 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).
>
> Best wishes,
>
> Will.
> Michiru Makuuchi wrote:
>
>> Hi,
>>
>>
>> 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
>>
>> Michiru Makuuchi
>> Max Planck Institute
>> for Human Cognitive and Brain Sciences
>> Stephanstrasse 1a, 04103 Leipzig, Germany
>>
>>
>>
>
>
>
> ------------------------------------------------------------------------
>
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