Dear Colleagues,
I'm using version 3.02 to run a two level negative binomial model. There seems to be a difference between the algebraic notation for the level 1 variance displayed in the equations window and the notation in teaching materials referencing earlier versions of mlwin and more generally in the literature.
In 3.02 I see..... pi + pi^2*a
Elsewhere I see.... pi + pi^2/v
Is this a bug or is there another explanation?
Many thanks,
Liam
Algebraic notation for variance in negative binomial model

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 Joined: Mon Oct 19, 2009 10:34 am
Re: Algebraic notation for variance in negative binomial model
Hi Checked this with Professor Kelvyn Jones who initially requested the change in notation and he provided the following explanation:
The equation is now correct there are two ways of doing this and we have always estimated it this way but the specification used to be incorrect
It is what Hilbe calls NB2
https://www.encyclopediaofmath.org/imag ... t_data.pdf
“This form of negative binomial has been termed NB2, due to the quadratic nature of its variance function “
NBD2 has 2 parameters for the level1 variance; that is quadratic level1 variance,
α is the overdispersion parameter; if α > 0 then NBD; if α=0, NBD reduces to Poisson;
in stored model results α estimate is associated with Bcons2.1 label
Lips data
And results