Hello Alistair,
You are correct.
ASREML reports the se(herit) and se(Gcorr)
not their variances.
I'll fix the manual.
Arthur
> From: Alastair Currie <A.J.Currie@massey.ac.nz>
> To: ASREML Discussion group <asreml@ram.chiswick.anprod.csiro.au>
> Subject: Variance or S.E. of heritability?
> Date: Tue, 28 Jul 1998 10:35:59 +1200
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>
> Hi,
>
> I was getting large variances for the heritability estimated by
> ASREML (PVS file) so I decided to work through the equation in the manual
> by hand to
> understand it better. I also compared the results with Dickerson's
> method cited in Dieters et al. (1995) T.A.G. 91:15-24. Dieters et al.
> claimed that Dickerson's method gave similar results but slightly more
> conservative (larger) than the Taylor method (used in ASREML).
>
> The results were:
>
> ASREML Var(herit) = 0.155 SE(herit) = 0.393
> Hand calc Var(herit) = 0.024 SE(herit) = 0.155
> Dickerson's Var(herit) = 0.032 SE(herit) = 0.179
>
> Dickerson's method was more conservative than the hand calculation as
> reported by Deiters et al but the ASREML output in the PVS file was much
> larger and looks like the S.E. and not the variance as stated in the
> manual.
>
> Can someone help me with this?
>
> The data I used for the hand calculations was extracted from the relevent
> ASREML files and is included below for your information.
>
> Variance components from the ASR file:
> Source Model terms Gamma Component Compnt/StndErr
> Trait.Family 225 69 0.246797 428.667 2.95
> Trait.Site.F 450 130 0.147830 256.769 3.11
> Variance 2108 1723 1.00000 1736.92 28.45
>
> Phenotypic variance = 2422.356
>
> From VVP file:
> Variance of Variance components
> 21082.6
> -3608.44 6822.36
> 21.4726 -408.195 3726.72
>
> Variance of Phenotypic variance = 23641.355
>
> Herit = 3*FamVar / PhenVar (coefficient of relationship between full and
> half-sib)
>
> Thanks,
> Alastair
<><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
Arthur Gilmour PhD email: Arthur.Gilmour@agric.nsw.gov.au
Senior Research Scientist (Biometrics) fax: <61> 2 6391 3899
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