Programming the statistical procedures from SAS

Negative individual predicted probabilities were identified in the final model fit

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Frequent Contributor
Posts: 111

Negative individual predicted probabilities were identified in the final model fit

Hello,

I want to perform a generalized ordered logit regression to predict education in 3 levels (edu3) with a set of variables. I tried this:

 

proc logistic data=edu.educationClean;
class  Langue(ref='0') cntr_regr(ref=first) genstat3(ref='0') eduM3(ref='2') religion(ref='0') /param=ref;
model edu3(descending)= cntr_regr lncohort cntr_regr*lncohort Langue genstat3 religion eduM3/unequalslopes maxiter=500 rsquare;
weight pond2 / norm;
by EU15 sex;
run;

However, I got this warning message:

WARNING: Negative individual predicted probabilities were identified in the final model fit.  You
         may want to modify your UNEQUALSLOPES specification.
WARNING: The LOGISTIC procedure continues in spite of the above warning. Results shown are based
         on the last maximum likelihood iteration. Validity of the model fit is questionable.

 

When I look at the results, they look consistent. What does that mean exactly? How can I fix the problem? I also ran a multinomial logit model on the same dataset and there were no message like this.

 

Thank you.

Super User
Posts: 10,020

Re: Negative individual predicted probabilities were identified in the final model fit

Posted in reply to Demographer

1) Remove   UNEQUALSLOPES 

2) variable EDU3 has value like 1 2 3?

Frequent Contributor
Posts: 111

Re: Negative individual predicted probabilities were identified in the final model fit

[ Edited ]

1) I need this statement, because I want 2 set of parameters for all variables.

2) Values are 0-1-2

Super User
Posts: 10,020

Re: Negative individual predicted probabilities were identified in the final model fit

Posted in reply to Demographer

That is weird. LOG said you got negative predicted prob, that doesn't make any sense .

Try remove "

weight pond2 / norm;  

or use 

freq pond2;

Frequent Contributor
Posts: 111

Re: Negative individual predicted probabilities were identified in the final model fit

Same message.

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