[ADMB Users] help with glmm.admb negative binomial multilevel model

Matthew Kraft mak251 at mail.harvard.edu
Thu Sep 22 18:40:44 PDT 2011


I am struggling to understand the syntax for fitting a negative binomial
multilevel model using glmm.admb.  I have conducted a cluster-randomized
trial with longitudinal data where students are nested in classes and
observations over time are nested within students.  My outcomes have a
negative binomial distribution.

I would like to fit a model where I model Y = Treat with nested random
effects for classes and students.

my question:

1) in the random statement how do I specific multiple nested random
effects?   Is is random= ~class: student

2) I don't understand the "group" argument.  The documentation say that this
is a string naming the main nesting variable.  Would that be students or
classes in my case?  When it says it must be a factor what does that mean?

My general thought is to specify the model as

output <- glmm.admb(Y~Treat, random=~class: student ,
group="???",family="nbinom", data=mydata)

Any specific help you can provide about coding would be greatly appreciated.


Matthew Kraft
Doctoral Candidate in Quantitative Policy Analysis
Harvard Graduate School of Education
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