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08-07-2016 09:54 PM

The logit model part of a ZIP model models the extra zeros as the outcome, but my client wants the probability of a count greater than 0 instead. Is it appropriate to do 2 completely separate models - a proc logistic modeling count>0 and a proc genmod with the zeros excluded modeling the count part?

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08-08-2016
11:53 AM

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Posted in reply to proctice

08-08-2016 11:52 AM

You can invert odds ratios by using the EVENT= option on the response variable on the MODEL statement.

Instead of

**model y(event="0") = x1 x2 x3;**

you can invert the odds ratio by using

**model y(event="1") = x1 x2 x3;**

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Posted in reply to proctice

08-08-2016 05:49 AM

I think I would stick with the ZIP model. You can use GENMOD or PROC FMM. The model will predict the probability of a zero count, which is P(Y=p | x). The client wants "one minus that predicted probability": 1 - P(Y=0| x)

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Posted in reply to Rick_SAS

08-08-2016 11:45 AM

They are more interested in the odds ratios being in the right direction, can I just invert them?

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08-08-2016
11:53 AM

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Posted in reply to proctice

08-08-2016 11:52 AM

You can invert odds ratios by using the EVENT= option on the response variable on the MODEL statement.

Instead of

**model y(event="0") = x1 x2 x3;**

you can invert the odds ratio by using

**model y(event="1") = x1 x2 x3;**