I have an event-related design with two tasks and an explicit baseline intermixed across three runs per person. For both tasks I am interested in later on remembered and/versus forgotten trials and I want to compare two groups of people.
This is the set-up of my analysis:
1. First-level analysis separately for each person and run setting up the basic contrasts (e.g., remembered vs forgotten trials for each task separately and remembered vs baseline, forgotten vs baseline etc.)
2. Higher-level analysis separately for each person where I combine the three runs, FE - one-sample t-test - this leads to all copes from the first level analysis turn into .feat files (e.g., remembered vs forgotten)
To have a match between the analysis and the graphical illustration, when I am plotting PSC for remembered and forgotten trials - as these are always contrasted with the baseline – I conducted the following alternative higher-level analysis:
3. Higher-level analysis separately for each person contrasting two cope.feat files (A vs Base and B vs Base) from the first Higher Level analysis (see 2.) using a FE - two group paired t-test, leading for example to a for example this cope ([remembered > baseline] > [forgotten > baseline])
I expected the results to be the same between 2. and 3. but they are very different and I don’t understand why this is the case and what’s the right way to go. Can anybody help me with this?
Thanks for your help!
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