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Abstract
The detection of heterogeneous variance across herd groups is based largely on data stratified by mean herd production. Such stratification is analogous to selection on herd means. This introduces the possibility of biased estimates of genetic and residual variances. Results presented show that Henderson's Method 3 estimates of the residual variance are unbiased by selection on herd means. However, reductions in sums of squares for sires have different expected values in no selection and selection models. The magnitude of this bias is evaluated with a small-scale simulation. Extension of these results to other methods of variance estimation reveals a potential bias from selection on herd means.
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Article info
Publication history
Accepted:
October 19,
1988
Received:
August 8,
1988
Identification
Copyright
© 1989 American Dairy Science Association. Published by Elsevier Inc.
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