I was wondering about the design of an experiment.
Lets say I have 2 scanning sessions. In both sessions there are conditions
A and B resulting in:
1A 1B 2A 2B
Between the scanning sessions I need to give the participants a different
set of instructions for how to act during the session e.g.
Instruction A, start scanning 1A 1B, stop scanning, Instruction B, start
scanning 2A 2B.
The participants would stay in the scanner for the 2nd set of instructions.
I would also counter-balance and participant 1 would have instruction A
then B and participnat 2 would have instruction B then instruction A.
I can't counterbalance within participants - the design has to be between
The effect of the instructions on condition A is the effect of interest.
My question is: when I set up my GLM model can I have 4 columns (1A 1B 2A
2B) and compare 1A to 2A (and vice versa)?
I ask because I would be comparing across sessions - but with a
counterbalanced design I hope this will be viable?
There doesn't seem to be any other way to do the experiment.