Okay, so the suggestions made to me included either performing a multiple
regression with columns for diagnosis, treatment, and the interaction, or
performing a one-way ANOVA with 4 conditions.
What do SPMers think is the more appropriate way to get close to a 2-way
ANOVA result?
In the regression case with 3 columns:
first: 1's for Drug, -1's for Placebo
second: 1's for Patients, -1's for Controls
third: first*second interaction
If I do a T-contrast of [1 0 0] that should show activations where Drug was
greater than Placebo correct?
what about a T-contrast of [0 0 1]? Is that (Drug > Placebo) AND
(Patient > Control), or does it just show areas where there was a
differential effect of treatment based on diagnosis (without letting me
know the direction)?
For the One Way ANOVA with 4 conditions:
Condition 1: Patients_Drug
Condition 2: Patients_Placebo
Condition 3: Controls_Drug
Condition 4: Controls_Placebo
In order to get for example (Patients > Controls) AND (Placebo > Drug)
would I use a T-contrast of [-1 1 1 -1]? (basically doing a double
subtraction, (-1 +1) - (-1 +1))
Thanks
-Mike
At 10:55 AM 7/27/2005 -0400, Andrew J. Saykin wrote:
>Mike,
>
>You could also use a regression model with main effects for diagnosis and
>treatment and include an interaction term for diagnosis X treatment
>effects since these are likely of particular interest in your study. As
>an example, we used this approach in our donepezil study (Brain 2004;
>127:1574-83).
>
>Andy Saykin
>
>
>
>At 10:23 AM 7/27/2005, Mike Angstadt wrote:
>>Hi,
>> We're looking for the best way to analyze a design like the
>> following:
>> - Two groups of subjects (ex: patients and controls)
>> - two levels of treatment (ex: drug and placebo)
>> Each subject has 2 scans from separate days. One for the drug
>> condition and one for placebo. What's the easiest and/or best way to
>> look at the group RFX?
>> One idea we had was to just model both scans in one large design
>> matrix (as in this post
>> http://www.jiscmail.ac.uk/cgi-bin/wa.exe?A2=ind0502&L=SPM&D=0&I=-3&X=334B9904DDB400BF3B&Y=&P=15311)
>> But we weren't sure if that was the best way.
>> Since SPM2 doesn't offer a 2-way ANOVA, what's the best option
>> to run something like that? Is there a script someone has to make SPM2
>> do a 2-way? Or could I fake it with a one-way ANOVA with 4 conditions
>> (ex: patient_drug, patient_placebo, control_drug, control_placebo)?
>>
>> Thanks
>>
>>-Mike
>
>
>
>========================================================
>Andrew J. Saykin, PsyD, ABPP
>Professor of Psychiatry and Radiology
>Director, Neuropsychology Program and Brain Imaging Laboratory
>Department of Psychiatry - DHMC
>Dartmouth Medical School
>Lebanon, NH 03756
>
>Tel. (603) 650-5824
>Fax (603) 650-5842
>
>email:[log in to unmask]
>
>http://synapse.hitchcock.org
>
>========================================================
>
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