Dear Genevieve,
If the order of the regressors in the design matrix is:
[gifted_simple, gifted_complex, nongifted_simple, nongifted_complex]
then you can use a t-contrast [-1 1 1 -1]. To illustrate what drove the
significance at a given voxel, you can also define an F-contrast eye(4)
and use it for plot > contrast estimates and 90% CI.
As mentioned previously, the recommended way to test for the interaction
here would be to compute the difference complex-simple for each subject
and enter these contrast images in a two sample t-test.
Best regards,
Guillaume.
On 12/04/17 18:32, Genevieve Allaire-Duquette wrote:
> Hi,
>
> Is there a good example of a paper reporting the results of a full factorial analysis using one between subject factor and one within-subject factor? Ideally, each factor having 2 levels.
>
> I have found a significant interaction effect using a similar design in a study I'm conducting. I would like to understand what are the relevant t-test I should present to reveal the direction of the effect.
>
> Factor 1 - giftedness: gifted and non-gifted pupils
> Factor 2 - complexity of problems: simple and complex problems
>
> Ho= no diff
> H1= Gifted pupils showing more activation than non-gifted pupils in inferior frontal gyrus (IFG) for complex problems
>
> As predicted I found a significant effect between giftedness and complexity, and I would like to look at t-tests to understand the direction of the effect.
>
> May thanks for your help.
> Genevieve
>
--
Guillaume Flandin, PhD
Wellcome Trust Centre for Neuroimaging
University College London
12 Queen Square
London WC1N 3BG
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