I have run into a perplexing problem. I am using logit to analyze an outcome
variable (mid)
logit mid illibdem1 limdyn1 absdyn1 auth1 pers1 cwpceyrs_werner rel_cap
econ_dep1 econ_dep2 rel_energy allies if cat2_2==11 & exclude2==0 &
initiate~=2, cluster(dyad_id)
and get the following message about one of my explanatory variables (absdyn1):
note: absdyn1 != 0 predicts failure perfectly
absdyn dropped and 68 obs not used
Given that message, I ran a cross tab expecting to find a perfect
correlation. Instead, I found:
. tab x y if cat2_2==11 & exclude2==0 & initiate~=2
| y
x | 0 1 | Total
-----------+----------------------+----------
0 | 41,539 326 | 41,865
1 | 1,829 16 | 1,845
-----------+----------------------+----------
Total | 43,368 342 | 43,710
I would just force Stata to keep the variable using "asis", but I am also
running the Clarify ado commands-which will not work with "asis." I could
change my reference category to "absdyn" rather than the category I currently
exclude "libdem1." (The first 5 explanatory variables are part of a set of 6
mutually exclusive categorical indicators.) However, I am not sure if that is
the best solution.
Does anyone know why I get the above error message when the variable does not
appear to actually be a "perfect predictor"?
Thanks for your help,
Karen K. Petersen
Vanderbilt University
Department of Political Science
Box 1817 Station B
Nashville, Tennessee 37235
US
615-322-6226
[email protected]
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