Variance or S.E. of heritability?
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Variance or S.E. of heritability?


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

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 
  -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