Alternative Outlier Model
!OUTLIER
The !OUTLIER qualifier invokes a partial implementation
of research by Alison Smith, Ari Verbyla and Brian Cullis.
With this qualifier, ASReml writes
G-1u
and
G-1u/ sqrt(diag( G-1- G-1
CZZ G-1))
to the .sln file,
and
R-1e/ sqrt(diag( R-1- R-1
WC-1W' R-1))
to the .yht file,
and copies lines where the last ratio exceeds 3 in magnitude to the .res
file
and reports the
number of such lines to the .asr file.
This is definitely work in progress but is a better measure than
the simple 'outlier' report in the .res file.
That report is based on a simplistic variance calculated
directly from the residuals and so does not recognise any variance
heterogeneity structure which might be present/modelled.
While this !OUTLIER procedure is not fully validated, and a rigorus assessment criterion
has not been established, it is helpful in a general sense.
When an outlier is suspected, the
out()
model term function may be used to more formally assess it.
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