Hi,
Using FEAT, I have 3 EV's I want to model - Stimulus A (1 second duration)
Stimulus B (1 second duration) and stimulus C (5 seconds duration)
Stimuli A or B (randomised stimuli presentation, 20 stimuli each) is
presented every 30 seconds beginning at timepoint zero i.e 0, 30 , 60.
The third stimuli "C" is subject responses that I am not interested in but
want to put in as a co-variate. "C" occurs every 30 seconds (40 in total)
starting at 15 seconds: ie 15, 45, 75.
When I put in these three conditions as EV's I get the rank deficiency
message. However, when I code A and B as the same EV i.e simply one
stimulus every 30 seconds for the duration of the experiment and still
include "C" there isn't a problem. I don't understand why!? There are the
same number of stimuli with the same ISI and duration, just coded together.
Can someone explain?
Many Thanks for your help,
Steve.
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