Hi,
This makes sense, yes. If you are happy that the temporal derivative
is accounting for lag changes then you could simply compare models by
look at the zstat on the EV of interest for each model - or as you say
look at second-level stats for further confirmation.
Cheers.
On 9 Mar 2009, at 15:30, Vishwadeep Ahluwalia wrote:
> Thanks Steve! once i run the 1st level analysis using different
> models , i was planning on
> comparing the models by comparing the PE values extracted from an
> ROI after running the
> group analysis. Is this a valid approach? or is there a better way
> to do this. Also, i'm
> slightly confused about whether i should be using a temporal
> derivative at the 1st level if i
> want to compare various models. Please correct me if i'm wrong:
> Temporal derivative
> would absorb any differences in Onset latencies and so the model fit
> (and hence PE)would
> then be dependent only on height and shape of the response. So would
> you recommend the
> use of temp. derivatives considering i'm comparing models?
> Thanks!
> -Vishwadeep Ahluwalia
>
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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
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