Dear Prof Douglas,
I asked this before but I would like to understand what I am doing and also need your recommendation.
I have three conditions : squeezes at three different levels. My aim is that I want to use spm to enter them as a one condition and then enter the parametric response as a covariate regressor. This will allow me to check the effect of using high low and mid forces using for example the first order effects.
I am trying to find the best event design using optseq. I do not mind to make the stimuli close or far away from each other.
What I have is tr 2.5 and ntp 174 so the length of the scanner is 435s.
I tried different input:
Optseq --ntp 174 --tr 2.5 --psdwin 0 20 2.5 --ev 1 3 20 --evc 2 3 20 --evc 3 3 20 --nkeep 1 --tnullmin 2 --nullmax6
The question that I have what are the inputs that I should change in order to get the best design that answer my question? I mean I thought that I should focus in tge nullmin and max. So in this. Case does increasing the null max make the design better. Also in term of the contrast should I look for it as a general term without including any contrast since I will enter them as one condition or should I see the effects of rest [1 1 1]
Any tip or advice that I should look at and change?
Lastly, if I would like to compare different designs, should I compare just the eff result ?
Thanks
AS