Dear Anson,
I am afraid you are asking for help at a too basic level for us to be
able
to help over email. You could look at our Web page for links to
tutorials
that will help. Usually, people learn to use SPM by being taught by
someone
with established experience. Alternatively, you could attend one of
the
SPM Short courses that are run around the world on a yearly basis.
I note
that you are in Hong-Kong. You could email the help list and find
out if there
is anyone else in Hong Kong using SPM that could help? (I am copying this
to
the list to see if there is anyone)
With very best wishes - Karl
Thanks a lot for your reply. It
helps me a lot. I want to ask you some more.
have 2 scans, one is pre treatment scan, one is post treatment scan. I
would
like to see whether the treatment helps the subject, so I should use
t-test to
compare both of them, right? I find there is a t-test when I click the
'Basic
model' button, but I dont know the steps in doing the test, pls could you
teach
me?
Many many thanks,
Anson
Quoting Karl Friston <[log in to unmask]>:
> Dear Anson,
>
> >I have a confusion here. I have 2 scans, one is acup, one is
motor.
> >I would like
> >to see their common activation sites. Should I use conjunctive
analysis.
>
> Yes, this would be appropriate. Note that SPM99 only tests the
conjunction
> null. This means you should make it clear that your inference
is based on
> the minimum t-value (and does not necessarily mean both t-tests are
> significant)
>
> >If so, I would like to confirm the way I am doing it is right. I
defined 4
> >contrast: acup rest>active; acup rest<active; motor
rest>active and motor
> >rest<active. My friend taught me, when I want to do a
conjunctive analysis,
> I
> >should choose acup rest<active and than press the CTRL key on
the keybroad,
> to
> >choose motor rest<active. Is it right? (I am using SPM99 in
WinXP)
>
> Yes.
>
> >Or should I define a new contrast, e.g. acup vs motor -1 1 -1
1?
>
> No. This is the average of the rest>active over rest and
acupuncture.
> (i.e. the main effect of active minus rest). The conjunction is a
multi-
> variate test that requires both contrasts to have a t-statistic that
is
> greater than some minimum value
>
>
> I hope this helps - Karl
>
--
Anson C. M. Chau
Instructor in Radiography
Family Dentistry and Endodontics
Faculty of Dentistry
The University of Hong Kong
