Hi - Not sure, depends on the details. I would expect that you would be
able to do the multiple equivalent runs and within-subject paired t-test
at second level, and then across all subjects (including cross-groups?) at
the third level.....?
Cheers.
On Tue, 29 Jun 2004, Robin Goldman wrote:
> How would you set this up? My understanding is that for a standard
> multi run, multi subject experiment it would be a 3 level analysis
> (run, subj, group). True? So if I want to do a paired t-test within
> subject across runs (8 nov1 runs vs 8 nov2 runs per subj) how would I
> set this up? I figured I'd have to do a second level paired t within
> subject using the 8 vs 8 copes... Ah! here's where my brain fuzzed
> before and added a non-existing level. The paired t-test yields the
> subj map, so all it needs is a further level three group. I assume this
> is what you were getting at.
>
> Best,
> Robin
>
> On Jun 29, 2004, at 5:03 AM, Stephen Smith wrote:
>
> > Hi - you don't need to worry about this at all - multiple comparison
> > corrections are with respect to _questions_ (ie final thresholdings)
> > and
> > not whatever (non-thresholding) stages led up to the final test. So
> > having multiple levels doesn't contribute to a MC problem.
> >
> > Cheers.
> >
> > p.s. - are you sure you need all the levels - for example, it may be
> > possible to include the nov1&2&3 and cross-run model in a more complex
> > second-level within-subject model.
> >
> >
> >
> > On Fri, 25 Jun 2004, Robin Goldman wrote:
> >
> >> Hi,
> >>
> >> Back with a question about analyzing the repeated novelty data (read
> >> below for details). We've
> >> decided to pair the runs that have the same stimuli (so, the Nov1 run
> >> with it's matched Nov2 run).
> >> This means that in addition to doing a straight forward first (run),
> >> second (subject), and third
> >> (group) level analysis I will also be doing a second level paired
> >> t-test of the Nov1 copes vs the
> >> Nov2 copes within subject, then a third (subject) and fourth (group)
> >> level for these copes.
> >>
> >> My question is this -- when you do the higher level analysis, do you
> >> take the number of tests into
> >> account for significance of the maps? If so, how do I adjust this for
> >> the fact that I'm doing a set of
> >> contrasts outside the normal analysis chain?
> >>
> >> Thanks.
> >> Robin
> >>
> >> On Fri, 2 Apr 2004 16:46:53 -0500, Robin Goldman
> >> <[log in to unmask]> wrote:
> >>
> >>> Hi there,
> >>>
> >>> New day, new question. We're running an event related novelty oddball
> >>> study. (Give people a task, surprise them every now and then with a
> >>> "novelty" event (Nov1) that is always something new, after a while,
> >>> in
> >>> another run, repeat some of these novelty events (Nov2) to see what
> >>> happens). We scan the subjects over multiple runs (12). All of these
> >>> contain Nov1 events, all but the first contain Nov2 events. (None of
> >>> the novelty events are repeated in the same run, only in later ones).
> >>>
> >>> So here's the question. It seems to me there are a number of ways to
> >>> analyze this data to see if there is a difference between first time
> >>> and repeated novel events (Nov1 vs Nov2).
> >>>
> >>> 1. In all but the first run (where there are no Nov2), model an EV
> >>> that
> >>> gives some relationship between the Nov1 and Nov2 events. But I don't
> >>> want to a priori do this.
> >>>
> >>> 2. Have one EV for Nov1 and one EV for Nov2, do a contrast within
> >>> each
> >>> run (all but run 1) of Nov1 vs Nov2. Then do a second level within
> >>> subject of this cope, then a third level across subjects.
> >>>
> >>> 3. Have one EV for Nov1 and one EV for Nov2. Do a contrast for each
> >>> EV.
> >>> Do a second level analysis within subject of the Nov1 contrast and
> >>> also
> >>> the Nov2 contrast (so, 12 copes for Nov1 and 11 for Nov2). Do a third
> >>> level within subject of the Nov1 cope vs the Nov2 cope. Then a fourth
> >>> across subjects. (As I'm writing this, I'm sure this is not the way
> >>> to
> >>> go...)
> >>>
> >>> So perhaps I answered my own question... thoughts?
> >>>
> >>> thanks again.
> >>> Robin
> >>>
> >>> ________________________
> >>> Robin Goldman, Ph.D.
> >>> Hatch Center for MR Research
> >>> Columbia University
> >>> 710 W. 168th Street, NIB-1
> >>> New York, NY 10032
> >>> (212) 342-0867
> >>
> >
> > Stephen M. Smith DPhil
> > Associate Director, FMRIB and Analysis Research Coordinator
> >
> > Oxford University Centre for Functional MRI of the Brain
> > John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK
> > +44 (0) 1865 222726 (fax 222717)
> >
> > [log in to unmask] http://www.fmrib.ox.ac.uk/~steve
> >
> >
> ________________________
> Robin Goldman, Ph.D.
> Hatch Center for MR Research
> Columbia University
> 710 W. 168th Street, NIB-1
> New York, NY 10032
> (212) 342-0867
>
Stephen M. Smith DPhil
Associate Director, FMRIB and Analysis Research Coordinator
Oxford University Centre for Functional MRI of the Brain
John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK
+44 (0) 1865 222726 (fax 222717)
[log in to unmask] http://www.fmrib.ox.ac.uk/~steve
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