Proc GENMOD: Error: Negative Binomial dispersion parameter too large to continue

[Saugata]

Hi All,

I am new to Proc GENMOD. Sometimes when I execute this procedure it gives an error Negative Binomial dispersion parameter too large to continue. At other times it executes perfectly. I do not have any idea about the problem or what is the meaning of the error. Below is the code I am using:

ODS SELECT NONE;
proc genmod data=&indsn.  ;                        

model var1 = var2/ dist=nb link=log;

output out    = &outdsn.                        

pred      = EXACT_1 ;

Run;

Quit;

ODS SELECT ALL;

I am using SAS 9.3 now, previously in SAS 9.1.3 I have never faced this problem. Is there a change in the procedure for 9.3? If not then what may be the problem.

Any help is appreciated.

Thanks in advance for your help.

Regards,

Saugata Mukherjee.

[SteveDenham]

If this is the same data that gave an answer in 9.1.3, then I would first check what values for the dispersion parameter were obtained under 9.1.3 and see if they were reasonable.  If the parameter values were reasonable, then I strongly suggest opening a ticket with SAS Technical Support, as radical changes were not implemented in the algorithm between 9.1.3 and 9.3, that I know of.

Steve Denham