Hi,
It does not work, too.
Former, using [-1 -1 1] worked also well.
Best
Auer, Tibor
-----Original Message-----
From: Jacqueline Griego [mailto:[log in to unmask]]
Sent: Wednesday, May 30, 2007 5:09 PM
To: [log in to unmask]
Subject: Re: [SPM] using t-contrast in ANOVA
Hi, I had a similar problem and maybe this will help yours--for some
reason SPM would only take it defined as [-.5 -.5 1]
Cheers
>>> "Auer, Tibor MD." <[log in to unmask]> wrote on 5/30/2007 11:05
AM:
> Hi
>
> Thank you for your help.
> I did not mean F is a bug. I meant defining t-contrast [-1 -1 2] or
[-1
> -1
> 1] worked well before. Now it does not. I can define t-contrast,
> however,
> with two columns (e.g.: [-1 0 1]), but with three I cannot.
> I know these other opportunities (f-test, conjunction). I am just
> curious
> what is the problem with this kind of t-contrast I want to use.
>
> Best,
>
> Auer, Tibor M.D.
> PhD-student
> University of Pécs, Medical Faculty
> Department of Neurosurgery
> Rét u. 2, Pécs, H-7623, Hungary
> Tel.: +36-20-986-9341
> E-mail: [log in to unmask]
>
>
>
> -----Original Message-----
> From: cyril pernet [mailto:[log in to unmask]]
> Sent: Wednesday, May 30, 2007 4:41 PM
> To: Auer, Tibor MD.; SPM
> Subject: Re: [SPM] using t-contrast in ANOVA
>
> Hi there,
>>
>> Dear SPM-ers,
>>
>> I have set up an ANOVA-design with three levels (see Design Matrix
>> attached), and I try to calculate a T-contrast to "substract" the
>> fisrt two levels from the third [-1 -1 2].
>>
>> With former revision of spm worked well, but now it says 'trying to
>> define a t that looks like an F'.
>>
>> Is it a bug, or did I something wrong?
>>
> Not sure but I guess it a feature :-)
>
> Unless you have strong hypothesis on the effect size of the col 3
(col3
> > than average col1 and col2) you would perform an F like [-1 0 1; 0
> -1
> 1] which tests if col3 is > col1 and/or col2 - or if you want even
> stronger do [-1 0 1] and [0 -1 1] and perform a conjunction null =
> col3>col1 AND col3>col2
>
> Hope this helps
> cyril
Jacqueline Griego, PhD
MPRC
Functional Neuroimaging Lab
PO Box 21247
Baltimore, MD 21228
Phone: 410.402.6030
FAX: 410.402.6077
[log in to unmask]
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