Dear All,
I'm carrying out some poisson GLMs on the number of eggs from starling
nests and want to know if there are any significant differences in the
mean number of eggs each year.
Ideally in poisson models one would want the residual deviance to be
close to the residual df indicating correct specification of the Poisson
model.
Usually in biological situations the residual deviance is much greater
than the residual df and this can be got round by estimating a dispersal
parameter from the data.
However, in this case I have the residual deviance/df ratio of 0.148
This affects the significance of terms in my final model as error bars
on the predicted means are considerably smaller
Could any one offer any advice on which to use, is 'under dispersion' a
valid concept?
Many thanks in advance
Guy
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Guy J. Forrester Phone: 01453 860777
CSL Research Unit Fax: 01453 860132
Woodchester Park e-mail: [log in to unmask]
Nymsfield
Stonehouse
Gloucestershire
GL10 3UJ http://www.csl.gov.uk
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----------------------------------------------------------------------
Guy J. Forrester Phone: 01453 860777
CSL Research Unit Fax: 01453 860132
Woodchester Park e-mail: [log in to unmask]
Nymsfield
Stonehouse
Gloucestershire
GL10 3UJ http://www.csl.gov.uk
----------------------------------------------------------------------
Disclaimer
The information contained in this message may include privileged,
proprietary or confidential information. Please treat it with the same
respect that you would expect for your own information. If you have
received it in error, we apologise, and ask that you contact the CSL
sender immediately and erase it from your computer. Thank you for your
co-operation.
Further information on confidentiality of our communications, can be
found at http://www.csl.gov.uk/email.htm
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