Hello...
I have a question. I am using binary logit to analyze an outcome
variable (formal).
When I enter the following string:
logit formal highfaci highform highman xpower xpowform xpowmanip viol pc
period1 period2 period3 period4 cmgoal
I get the following message about one of my explanatory variables
(xpowfaci):
note: xpowfaci != 0 predicts failure perfectly
xpowfaci dropped and 11 obs not used
I understand that this message is telling me that there is a perfect
correlation occurring with this variable. This "xpowfaci" variable is
an interaction term of two of my other explanatory variables --
"highfaci" and "xpower."
My question: Is it proper to still include the eliminated variable --
"xpowfaci" -- in the equation and report the results with these 11 cases
dropped, or should I re-run the logit excluding "xpowfaci" from the
equation completely? I notice that the coefficient on one of my other
explanatory variables -- "highfaci" -- changes radically depending on
whether or not I include "xpowfaci" in the equation.
Thank you!
David Quinn
Department of Government and Politics
University of Maryland, College Park
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