@sld, Thanks for your help. I haven't read all of the links that you have provided yet, but to answer some of your questions, my actual dataset has 67 observations. Yes, I have some subjects that I have only one observation for, and others that I have 2 or 3 observations. The instances of PMN>TNCC is an accident of the random data I used. This does not occur in my data set. Yes, I am happy to fit a random intercept model. I have included the random _residual_ statement due to apparent over dispersion. Thanks! Katy
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