Dear SPM experts,
I am having trouble setting up my second level analysis.
In short, I have 18 subjects for which multiple sessions were acquired. After having filtered out sessions not fulfilling the predefined performance criterion, the number of repeated measurements differs strongly between the subjects (varies from 1 to 5 sessions).
I considered the following approaches to solve the issue:
1. Modelling the subject factor by adding all sessions of the same subject in one first level analysis (averaging the sessions). A potential drawback comes up when I go on with the second level analysis. Each contrast map from the first level analysis would be taken into account in equal measure, no matter the number of repeated measurs for each subject.
2. I performed a first level analysis for each session and took all contrast maps into the second level. Additionally, I defined a multiple covariate including a binary regressor for each subject with at least 1 session. The regressors assign the contrast maps to the respective subject. You find the desgin matrix in the attachment.
3. A flexible factorial design?
What is the best way to model the different number of repeated measures? Is my second approach (admittedly a very easy one) appropriate to handle my problem? is SPM even capable to cope with my study design?
Thank you in advance.
best,
Laurens
