Hello,
I have data from an event related reading experiment, where items from 3
conditions (words, pseudowords and a baseline – looking at a cross) are
randomly intermixed. I have two groups of participants: patients and
controls which I would like to compare using the 2nd level analysis using
SPM5. I would like to include 3 variables as covariates (defined as
nuisance variables), in my SPM5 analysis: ADHD Index (a score on the
standardised questionnaire), Dyspraxia Index (a score on a non-standardised
questionnaire, number of ‘yes’ responses) and % correct on the Post test.
The only experience with covariates and SPM analysis which I have to date
is with movement parameters (obtained in the Realignment stage of data
pre-processing) which I entered as multiple regressors when setting up a
Design Matrix. I presume that the ADHD, Dyspraxia and Post-test covariates
can be entered at this stage. Is this correct? However, what bothers me
here is the fact that in contrast to the motion parameters where, I think,
there was a covariate for each scan (or more precisely, a set of
covariates), here I have only one score (per covariate) per participant,
e.g. participant1 would have the following scores: 68, 17, 70.
I would be grateful for suggestions on how to enter such covariates into my
1st level analysis. Also I presume that one only does it in the 1st level
analysis and not in the 2nd level analysis?
Thank you very much for your help.
Agnieszka Reid, PhD
Aston University
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