Negative binomial v. ZINB: Plot probabilities

Posted by MLIves on Nov 08, 2018; 3:05pm
URL: http://spssx-discussion.165.s1.nabble.com/Negative-binomial-v-ZINB-Plot-probabilities-tp5736964.html

Good morning SPSS gurus!

 

We have an analysis using a propensity score (likely to be in inEMPS) split into quintiles to compare inEMP=1 to inEMPS=0.

We have run a Negative Binomial due to over-dispersion—but a question has been raised about why not a zero-inflated NB.

 

I have run both (using LOGISTIC and STATS_ZEROINFL) both overall and separately (split file for NB/select if in quintile for ZINB).

Now the question is: Which is better?  Since the AIC is only slightly lower for ZINB (around 30/>18000), I’ve been asked to

“plot fitted probabilities of the observed data under the zero-inflated and the non-zero inflated model against each other”

 

I hope someone can help me with the (best) way to get these plots (within quintile) for NB and ZINB. 

This is my first attempt at ZINB. 

 

Here is the syntax I used for both

 

*** ZERO INFLATED NEGATIVE BINOMIAL USING nBH_EDPre (NUMBER of PRE ED visits).

STATS ZEROINFL MODELSOURCE=ESTIMATE DEPENDENT=nBH_EDPOST COUNTMODEL=inEMPS LR3pred nBH_EDPRE

  SAMEREGRESSORS=YES

  COUNTDIST=NEGBIN ZEROLINK=LOGIT

  /OPTIONS STARTVALUES=GENLIN OPTMETHOD=BFGS MAXITER=1000 TOL=0.0000000001

  /SAVE DATASET=ZI_NB_n

  ID=CID

  WORKSPACEACTION=CLEAR.

 

**************************.

****  With N Pre.

**************************.

LOGISTIC REGRESSION VARIABLES AnyBH_EDPOST

  /METHOD=ENTER inEMPS

  /METHOD=ENTER inEMPS nBH_EDPRE

  /PRINT=GOODFIT CI(95)

  /CRITERIA=PIN(0.05) POUT(0.10) ITERATE(20) CUT(0.5).

 

--------------

Melissa Ives

 

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