Subject: | | Re: snpm5 |
From: | | Roberto Viviani <[log in to unmask]> |
Reply-To: | | [log in to unmask][log in to unmask]> > Subject: Re: 2nd level F test > > On Tue, 22 Apr 2008 20:07:31 +0100, Brian Essex <[log in to unmask]>=20 > wrote: > > >I have done an f contrast at the individual subject level and now > >would like to look at the effect of this contrast across subjects (2nd > >level/random effects). What is the correct way to do this? I cannot > find=20 > an > >F test in the 2nd level toolbox. > > > >Basically, what statistical test can I use to implement this and how can > I > >then define my contrast in the contrast manager? > > You don't take F test images to the second level (group level). You > only=20 > take con images. > > How easy it is to do F tests (or ANOVAs) at the group level depends on=20 > whether you're taking more than one con image per subject to the group=20 > level. If you do take more than one, it's a repeated measures design, > and=20 > while it can be done, it's a lot more complicated than if there's just > one=20 > image per subject. > > Best thing to do is search this list for advice, and also consult the=20 > manuscript "ANOVAs and SPM," by Henson and Penny: > http://www.fil.ion.ucl.ac.uk/~wpenny/publications/rik_anova.pdf > > >Thanks, > >Brian > >=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= > > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > > > -------------------------------------------------------------------------- > CONFIDENTIALITY NOTICE: This e-mail message, including any > attachments, is for the sole use of the intended=20 > recipient(s) and may contain confidential, proprietary,=20 > and/or privileged information protected by law. If you are=20 > not the intended recipient, you may not use, copy, or=20 > distribute this e-mail message or its attachments. If you=20 > believe you have received this e-mail message in error,=20 > please contact the sender by reply e-mail and destroy all=20 > copies of the original message > > ------------------------------ > > Date: Wed, 23 Apr 2008 15:17:08 +0100 > From: "Stephen J. Fromm" <[log in to unmask]> > Subject: Re: 2nd level F test > > On Tue, 22 Apr 2008 20:07:31 +0100, Brian Essex <[log in to unmask]>=20 > wrote: > > >I have done an f contrast at the individual subject level and now > >would like to look at the effect of this contrast across subjects (2nd > >level/random effects). What is the correct way to do this? I cannot > find=20 > an > >F test in the 2nd level toolbox. > > > >Basically, what statistical test can I use to implement this and how can > I > >then define my contrast in the contøN¦ |
Date: | | Tue, 1 Apr 2008 14:45:22 +0200 |
Content-Type: | | text/plain |
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Hallo,
may I ask what is permuted, the explanatory variable of interest
alone, or the variable of interest and nuisance covariates? I would
think that only the variable of interest should be permuted, but I
would be interested to hear if there is a rationale for permuting
variables of interest and covariates together, or if anyone has strong
opinions in one or the other direction.
We are currently using permutation tests in the statistical analysis
of our data, and permute the variable of interest only, so my question
also has a practical relevance. If no one cares, then we'll keep using
our approach.
Thanks a lot,
Roberto Viviani
Dept. of Psychiatry
University of Ulm, Germany
Quoting Thomas Nichols <[log in to unmask]>:
> Dear Johanna,
>
> No, currently the paired t-test plug-in in SnPM doesn't allow for nuisance
> covariates. However, a paired t-test is equivalent to a one-sample t-test
> on the pairwise differences, and the One Sample T-test plug-in *does* allow
> for nuisance (or "confounding") covariates.
>
> The attached script, PairDiff.m will produce the differences if you don't
> already have them. Let me know if it works for you OK.
>
> Sorry for the trouble.
>
> -Tom
>
> On Mon, Mar 31, 2008 at 11:13 AM, Scheuerecker, Johanna <
> [log in to unmask]> wrote:
>
>> Dear SPMers,
>>
>> does anyone know if there is a possibility to use paired t-test in SNPM5
>> with one covariate of interest?
>>
>>
>> Thanks a lot,
>>
>> Johanna
>>
>
>
>
> --
> ____________________________________________
> Thomas Nichols, PhD
> Director, Modelling & Genetics
> GlaxoSmithKline Clinical Imaging Centre
>
> Senior Research Fellow
> Oxford University FMRIB Centre
>
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