Hi,
Yes, this looks fine. In this design and set of contrasts there is no
need to ortho EVs 3 and 4 wrt 5 and 6 as this won't change the
contrasts.
Cheers, Steve.
On 24 Jan 2008, at 15:47, Yi-Shin Sheu wrote:
> Hello:
>
> This is my first time designing matrix and it will be very much
> appreciated if someone can give me
> some input or suggestion.
>
> I want to compare control vs. patient group and see if there is any
> brain region show gray matter
> reduction that can be explained by effective regressor (EV3:
> demeaned control group abuse score.
> EV4: demeaned patient group abuse score) after regress out confounds
> (ex: EV 5: demeaned
> control group age, EV 6: demeaned patient group age).
>
> Example:
> Abuse score for control: 5 7 12
> Abuse score for patient: 15 10 20
> Age for control: 10 12 14
> Age for patient: 12 14 16
>
> Design Matrix:
>
> EV1 EV2 EV3 EV4 EV5 EV6
> 1 0 -3 0 -2 0
> 1 0 -1 0 0 0
> 1 0 4 0 2 0
> 0 1 0 0 0 -2
> 0 1 0 -5 0 0
> 0 1 0 5 0 2
>
> ortho EV3 wrt to EV 5
> ortho EV4 wrt to EV 6
>
> Contrast:
> 0 0 1 -1 0 0
> 0 0 -1 1 0 0
>
> Will this design be able to answer my question?
>
> Kindly advise.
>
> Thank you very much.
>
> Yi-Shin
>
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Stephen M. Smith, Professor of Biomedical Engineering
Associate Director, Oxford University FMRIB Centre
FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK
+44 (0) 1865 222726 (fax 222717)
[log in to unmask] http://www.fmrib.ox.ac.uk/~steve
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