Programming the statistical procedures from SAS

proc genmod / inverse gaussian

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New Contributor
Posts: 2

proc genmod / inverse gaussian

Hello everyone,

By estimating the count data (number of claims per insured) with an inverse Gaussian distribution by the GENMOD procedure SAS, SAS does not take the zero (0) data. Indeed for the dependent variable (number of claims) many contract have a number of claims 0. when I execute the GENMOD procedure with a IG distribution (inverse Gaussian ) these data are not considered (Invalid Response Values).

how do I do in this case to ensure that SAS uses all data including where zero variable for the inverse Gaussian distribution?

thank you in advance

Nassima

Valued Guide
Valued Guide
Posts: 684

Re: proc genmod / inverse gaussian

You can't. The inverse gaussian distribution is only defined for nonzero positive values. Same for the gamma.

New Contributor
Posts: 2

Re: proc genmod / inverse gaussian

Hi, thanks

but I have found in the actuarial literature that the number of claims can be adjusted by an inverse Gaussian distribution

Valued Guide
Valued Guide
Posts: 684

Re: proc genmod / inverse gaussian

I would need to see what they did, because the IG is undefined at 0. One could model the data as a mixture of two distributions, with a different distribution for zeros. But you can only do this in Genmod with discrete distributions. Perhaps PROC FMM.

SAS Employee
Posts: 242

Re: proc genmod / inverse gaussian

If your data are counts, then you should consider using a discrete distribution rather than a continuous one.  Count data are typically modeled using Poisson, negative binomial, or zero-inflated versions of those distributions.  Those distributions allow zero values.  Models using these distributions can be fit using PROC GENMOD.

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