Dear Donald,
Thanks for the information. In the meantime, I received information from Michael Harms, who used a 2x4 ANOVA.
But it is great to see that I am doing it correctly and finally, I understand the design now. Fantastic!
Thank you
Best
Heidi
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Dr. Heidi Jacobs
Postdoc researcher
Faculty of Health, Medicine and Life Sciences
School for Mental Health and Neurosciences
Division Cognitive Neuropsychiatry and Clinical Neurosciences
Alzheimer Center Limburg
[log in to unmask]
www.maastrichtuniversity.nl
www.heidijacobs.nl
Dr. Tanslaan 12, 6229 ET Maastricht
P.O. Box 616, 6200 MD Maastricht, The Netherlands
T +31 43 38 84 090 F +31 43 38 84 092
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Van: FSL - FMRIB's Software Library [[log in to unmask]] namens MCLAREN, Donald [[log in to unmask]]
Verzonden: vrijdag 28 juni 2013 22:11
Aan: [log in to unmask]
Onderwerp: Re: [FSL] Overall F-test
Heidi,
There are several issues with your analysis:
(1) You need to include a subject factor in your model. To do this, add one column for each subject. The rows associated with that subject will get a 1, all other entries will be 0.
(2) Your contrasts are not valid for inference. As you have a within-subjects design, you can only interpret the within-subject effects in the model. All 3 contrasts you set up are between-subject contrasts (group 1 vs group 2). To get an estimate of the group difference, you should average the 3 time points and use a two sample t-test.
(3) Covariates, if entered properly, will not change your within-subject effects; therefore, its best not to enter them.
Hope this helps.
On Mon, Jun 17, 2013 at 7:30 AM, Jacobs H (NP) <[log in to unmask]<mailto:[log in to unmask]>> wrote:
Dear FSL-people,
I have fMRI data of 2 groups (each group 20 people) over 3 time points.
If I want to perform a repeated measures test with a within variable and a between-group variable, would the mat and con file be ok?
(G1_T1 = group 1, time 1)
I only have one T1-weighted image for person. How can I include grey matter as a covariate (I don't have 120 files) without harming the model?
Thanks
Heidi
================================================
Dr. Heidi Jacobs
Postdoc researcher
Faculty of Health, Medicine and Life Sciences
School for Mental Health and Neurosciences
Division Cognitive Neuropsychiatry and Clinical Neurosciences
Alzheimer Center Limburg
[log in to unmask]<mailto:[log in to unmask]>
www.maastrichtuniversity.nl<http://www.maastrichtuniversity.nl>
www.heidijacobs.nl<http://www.heidijacobs.nl>
Dr. Tanslaan 12, 6229 ET Maastricht
P.O. Box 616, 6200 MD Maastricht, The Netherlands
T +31 43 38 84 090<tel:%2B31%2043%2038%2084%20090> F +31 43 38 84 092<tel:%2B31%2043%2038%2084%20092>
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