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