Still Negative Maternal Variance
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Still Negative Maternal Variance



Hello:

With this .as file

Birth weight
 ani    !P 
 mat    !P 
 pe     6803
 sex    2 !A
 aod
 aod2
 sy     50 !A 
 AdG
 AdPH
 AdRA
 AdS
 AmS
 Dd
 Dm
 bw        
PE2_2.prn !MAKE
BW21.prn 
bw ~ mu sex aod aod2 sy AdG AdPH AdRA AdS AmS Dd Dm !r ani mat pe .254
0 0 1
ani 2 
2 0 US 1.16 .0 .287
ani

I got this estimates for variances and covariances:

 Source       Model  terms     Gamma     Component    Compnt/StndErr
  pe             6803   1572  0.781423E-03  0.805809E-02      0.02
  Variance       3132   3099   1.00000       10.3121         19.76
  ani         US=UnStr     1  0.311831       3.21562          5.15
  ani         US=UnStr     1  0.188442E-01  0.194323          0.64
  ani         US=UnStr     2 -0.207402E-02 -0.213874E-01     -0.06
  
I have two questions:

1) It is possible to obtain negative variance estimates with the REML
algorithm
used in ASREML? (i.e., this is something that you can expect in some
situations?) 

2) There is something wrong in my model setting that may explain the
negative estimate?

Thank you again

Hugo
================================
Hugo Montaldo
Research Fellow
Division of Animal Science
University of New England
Armidale, NSW 2351
Australia

Phone  61 2 67 733004
Fax    61 2 67 733275

E-mail hmontald@metz.une.edu.au
http://metz.une.edu.au/~hmontald/
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