SAS two-part model

[uzma03505621]

Hello everyone, 

 I am a new SAS user and I am using Medical Expenditure Panel Survey( MEPS) for my research. I have to use a Two-part model to study the impact of various independent variables on my dependent variable ( COST). Can someone please help me with the SAS SYNTAX for the two-part model.

[mkeintz]

I am unfamiliar with the term "two-part model".  Can you describe?

[uzma03505621]

It's a statistical method used when the expenditure data is not normal I.e. it can be rightly skewed or with excess zero expenditures. So the first part involves a binary logit model to differentiate positive and zero expenditures and the second part of the model involves a glm model with gamma distribution and link function.
I'm attaching the link to the article I used as my reference :
https://scholarworks.gvsu.edu/fsdg/556/

[StatDave]

These are zero-inflation models which are in the class of finite mixture models as can be fit using PROC FMM. While there is some question of the appropriateness of doing this with a continuous distribution like gamma, the following code is an example with single predictor, G, and will provide a model fit and predicted values.

proc fmm data=a plots=density(nbins=9);
   class g;
   model y = g / dist=gamma;
   model   +  / dist=constant;
   probmodel g;
   output out=fmmpred pred;
   run;

[uzma03505621]

Can you share any source for me to interpret the output of this code?

[Rick_SAS]

The Getting Started examples in the documentation often explain how to interpret the results.

[Season]

I am also interested in building this kind of model. Could you please explain why there it might be inappropriate to build such models for continuous distributions in more detail? Thank you!

[StatDave]

...but perhaps a better, and more easily interpreted, model is the Tweedie model that can be fit in PROC GENMOD with the DIST=TWEEDIE option. The Tweedie distribution can model a nonnegative response with a mass at zero, so it is often used to model cost when there can be a set of zero values. The output is much like an ordinary gamma model since it isn't a "two part" model.

[Ksharp]

As @StatDave said it is a zero-inflation model generally suited to COUNT data ,not a continous data.

Check this brand-new session:

https://communities.sas.com/t5/SAS-Communities-Library/Making-Zero-Inflation-Count/ta-p/962019/jump-...