I
am trying to run a logistic regression and when I do I get the following errors…
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For
split file Unit = Hal 5 and Hal 6, there are 419 (39.1%) cells (i.e.,
dependent variable levels by subpopulations) with zero frequencies.
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For
split file Unit = Hal 5 and Hal 6, unexpected singularities in the Hessian
matrix are encountered. This indicates that either some predictor variables
should be excluded or some categories should be merged.
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The
NOMREG procedure continues despite the above warning(s). Subsequent results
shown are based on the last iteration. Validity of the model fit is
uncertain.
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Now, the “zero
frequency” warning I have been ignoring because I needed to use the
zeros to calculate mean, so I am assuming they would be included in this type
of regression.
Where I am
really unclear is the “unexpected singularities in the Hessian matrix
are encountered. This indicates that either some predictor variables should
be excluded or some categories should be merged” warning. I am not sure
what it means or what I do to go about fixing it.
I would appreciate
any help anybody can give me.
Thanks,
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Amanda
Bertram, MS
Sr. Research Program Coordinator
Department of Medicine
Division
of General Internal Medicine
Johns
Hopkins Outpatient Center, Room 7164
601 North Caroline Street
Baltimore, MD 21287
410.955.1120 fax: 410.614.1195
[hidden email]
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