Suppose I have 2 EVs, context and noContext. Times of stimuli are given as
follows
NoContext 30
Rest 18
Context 30
Rest 18
NoContext 30
Rest 18
Context 30
Rest 18
NoContext 30
Rest 18
Context 30
Rest 18
NoContext 30
Rest 18
Context 30
Rest 18
NoContext 30
My primary goal is find where Context activation is greater than NoContext
activation.
Should I do 3 EVs, Context, NoContext and Rest? If so, I selected 3 EVs in
the full model setup, and defined three contrasts for "Real EVs" as follows
context vs Rest, 1 0 0 0 -1 0
NoContext vs Rest 0 0 1 0 -1 0
Context vs NoContext 1 0 -1 0 0 0
In this case, how would real EVs come into play?
Or should I do 2 EVs, Context and NoContext only? If so, I am unsure of how
to define contrasts. How should I define "Context vs Rest" contrast?
context vs Rest, 1 0 0 0 (Method 1)
context vs Rest, 1 -1 1 0 (Method 2)
Or for that matter, the "NoContrast vs Rest" contrast?
NoContext vs Rest 0 0 1 0 (Method 1)
NoContext vs Rest 1 0 1 -1 (Method 2)
Or even more confusing, "Context vs NoContext" contrast?
Context vs NoContext 1 0 -1 0 (Method 1)
Context vs NoContext 2 -1 -2 -1 (Method 2)
If I choose (Method 1), how would the software distinguish between REst and
the other EV? And if I choose (Method 2), is my definition of the "Context
vs NoContext" contrast correct? Also, if (Method 2) is correct, what would
the contrast I defined in (Method 1) give me?
I guess my confusion comes partly from my lack of understanding of the
statistics behind this and partly from not knowing what "Real EVs" mean. I
would be very grateful if someone can please explain this to me. Thanks.
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