Dear WinBugs list,
A rather basic question from a novice, I'm afraid ...
I would like to be able to know the Deviance Information Criterion
(DIC) and associated measures (Dbar, Dhat, pD) for an age-period-cohort
poisson regression model I'm fitting (as per Bray, Appl Statist 2002,
which assumes autoregressive smoothing in the age, period and cohort
effects). The trouble I'm having is that the DIC option is greyed-out.
This is what I've been doing: I run a burn-in of 1,000 iterations on 3
chains. I "set" the DIC counter(inference -> DIC -> set). Then I run
another 1,000 iterations. The DIC option under the inference menu is
then greyed-out.
I've seen warnings that suggest DIC is either not calculated or
unreliable if the model has not converged, and that it cannot be
calculated for mixture models. But I don't think either of these
circumstances applies here (despite the fairly short burn-in).
What could be the problem? Is there anything I can do about it?
Dominic Muston
Cancer Screening Evaluation Unit
Institute of Cancer Research
Sutton, UK
Tel: +44 (0)20 8722 4467 (or x4467)
www.icr.ac.uk/cseu
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