Thanks Eugene,
Sorry, my mistake. Looking at the two set-ups I've realised that I had contrast masking selected for one analysis.
Thanks for your help.
Sarah.
-----Original Message-----
From: FSL - FMRIB's Software Library on behalf of Eugene Duff
Sent: Wed 5/05/2010 7:33 PM
To: [log in to unmask]
Subject: Re: [FSL] results change with number of contrasts
Hi Sarah -
They shouldn't be any different. Perhaps try running a "diff" command on
the design.fsf files in the two output directories to see if there are any
differences in thresholding settings.
Also, I think it is just a typo, but you wrote out the covariate contrast
differently the 1st and 2nd time..
Cheers,
Eugene
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On 5 May 2010 05:20, Sarah <[log in to unmask]> wrote:
> Hi,
>
> I'm running a higher-level Flame 1 analysis using FEAT v5.98. The
> group-level analysis is for 30 participants, I have two EV's (Mean
> activation and 1 covariate of interest, covariate orthogonalised wrt mean),
> and I'm testing a number** of contrasts using cluster correction, z
> threshold 2, p threshold 0.05.
>
> **Depending on how many contrasts I run, I get different results. For
> example, with two contrasts:
> Mean +1 0
> Covariate1 0 +1
> I get significant activations for both contrasts. But, if I add further
> contrasts, eg:
> Mean +1 0
> Mean -1 0
> Covariate 0 +1
> Covariate 0 -1
> Then my Mean contrasts result in significant activation, but neither of my
> covariate contrasts do.
>
> BUT, if I open up the zstat images resulting from these two analyses in
> FSLVIEW, they look identical at the same given z level.
>
> Can anyone offer advice??
>
> Thanks,
>
> Sarah.
>
>
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