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| Does anyone have a good example (i.e., sample MPlus code) of a zero-inflated poisson model using the TWOLEVEL RANDOM command? Thanks! |
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You can start with Example 9.2 and add:
COUNT = y (i);
and change the MODEL command as follows:
MODEL:
%WITHIN%
s | y ON x;
y#1 ON x;
%BETWEEN%
y s ON w xm;
y WITH s; |
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| Thanks Linda! One more question if you don't mind. When running my ZIP model MPlus obviously creates the binary variable (mine is alc#1). I assumed, but wanted to confirm, that this alc#1 variable takes the 0s from my original count variable (alc) and gives them 0s in alc#1 and anyone that has a non-zero value on alc gets a 1 for alc#1. |
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I am quoting from my ZIP post yesterday:
"In the binary part Mplus does logistic regression for Prob(u#=1), where u# is a binary latent inflation variable and u#=1 indicates that the individual is unable to assume any value except 0. This is called the zero class. "
So anyone who has a non-zero value on alc gets a 0 for alc#1. In other words, alc# (alc#=1) represents the inflation - the 0 part. |
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| Stella Resko posted on Wednesday, November 19, 2008 - 4:16 pm
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| I was wondering if anyone has a good example (i.e., sample MPlus code) of a zero-inflated poisson model that includes an interaction? Thanks! |
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| Do you mean interaction between 2 IVs? If so, you just use Define to create that interaction and use it as another IV. |
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Hello,
I was wondering if there is a limit on how many variables can be treated as count variables within a ZIP model? Can only endogenous variables be zero inflated for the model to converge?
Thanks!
Paige |
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Q1. No
Q2. Typically ZIP modeling is applied to DVs. After all, how would you formulate influence from a ZIP variable (that is, having the ZIP variable as an IV)? Treating the counts as a continuous variable would be unsatisfactory, I would think. |
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Dr. Muthen,
Thank you for your response! That helps.
Best,
Paige |
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