Hi
I have been unable to run a conjunction analysis using the within-subjects
ANOVA model
My problems seem to culminate at the contrast selection stage
I have no problem if I test run it using a between subjects design (I know
this was wrong, I was just testing it)
I know I have made a mistake at the model design stage or the contrast
selection stage but I don't know which
I have 15 participants that performed 3 different (and separate) tasks
Within each task I first compared condition 1v2 (comparison a), and
condition 1v3 (comparison b)
Having generated individual con images for each participant for each of the
3 tasks I then proceeded to the within-subjects ANOVA option
I entered the 3 comparison a con images (task 1, task 2, task 3) for subject
1, then subject 2 and so on
I wasn't 100% convinced that I might have broken the sphericity assumption,
but thought I'd go along with it anyway and selected the correction - was
this wrong?
By the phrasing of the next question I was a little confused as to whether I
should select repetitions across subjects or conditions. I selected subjects
(but to be honest it wouldn't work even when I tried it across conditions) -
was this wrong?
I said yes to the following correlation condition (from the list, if you
have selected a sphericity correction most people seem to be saying to go
ahead and automatically say yes to this) - was this wrong?
Parameter estimability was greayed out for all variables but I gather that
isn't actually a problem.
Now at the contrast manager stage, if I had run a between subjects ANOVA, I
used to enter '1 0 0' to determine the effects of task 1, '0 1 0' for task
2, and '0 0 1' for task 3
I'd then select all 3 together and hey presto i got my conjunction
In a within-subjects ANOVA when I entering '1 0 0' for task 1, I get and
invalid contrast error message
So have I made a mistake here too?
Thank-you for your valuable time
Regards
Rachel Mitchell
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Dr Rachel L. C. Mitchell
Lecturer in Cognitive Psychology, University of Reading
Honorary Research Fellow, Institute of Psychiatry
Research Psychologist, Berkshire Healthcare NHS Trust
Correspondence Address:
School of Psychology
Whiteknights Road
University of Reading
Reading
Berkshire
RG6 6AL
Tel: +44 (0)118 378 8523
Direct Dial: +44 (0)118 378 7530
Fax: +44 (0)118 378 6715
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