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> Date: Mon, 24 Sep 2001 10:41:22 +1000
> To: asreml@chiswick.anprod.csiro.au
> From: Kim Bunter <kbunter@metz.une.edu.au>
> Subject: Solutions for FE under link functions
> Mime-Version: 1.0
>
> Dear Arthur,
>
> when 0/1 data is analysed with the probit (or logit) link function, do the
> solutions for fixed effects have any meaning? For example, the following
> solutions are obtained for management groups under either animal (A) or
> sire (S) models, when assuming normality (N) or using the probit link
> function (P).
>
> AN SN SP
> 0.33 0.33 71.61
> 0.38 0.38 71.80
> 0.43 0.43 71.86
> 0.58 0.59 72.72
I would expect Fixed effects to be similar for Sire and Animal models when
assuming normality. I would expect the same pattern in the probit effects.
However, probit values of 71 seem way off scale.
0.33 translates to probit of -0.44
0.38 -0.315
0.43 -0.176
0.59 0.228
So something is wrong. It could be a problem of some fixed effects having
all observations in the same class. How complex is the model?
>
> What is the interpretation of these results, and why are SP values of such
> a different magnitude? The differences between solutions for each level
> also vary. Are computed F_values informative for modelling purposes when
> using the link functions?
>
The F_values are indicative but not strictly appropriate. The usual
testing strategy is to drop a term and test the
change in deviance (under a fixed model) as a Chi square.
The F_value is affected by the way n which over/under dispaersion
is handled.
> Any comments much appreciated.
>
> Cheers
>
> Kim
> Kim Bunter
> Research Scientist
> Animal Genetics and Breeding Unit
> University of New England
> Armidale, NSW, 2351
> AUSTRALIA
>
> Ph (ISD): -61-2-67733788
> Fax (ISD): -61-2-67733266
> email: kbunter@metz.une.edu.au
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Arthur Gilmour PhD mailto:Arthur.Gilmour@agric.nsw.gov.au
Principal Research Scientist (Biometrics) fax: <61> 2 6391 3899
NSW Agriculture <61> 2 6391 3922
Orange Agricultural Institute telephone work: <61> 2 6391 3815
Forest Rd, ORANGE, 2800, AUSTRALIA home: <61> 2 6362 0046
Cargo: <61> 2 6364 3288
I havn't finished building my house at Cargo but am back at work.
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