Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành y học dành cho các bạn tham khảo đề tài: Threshold models with heterogeneous residual variance due to missing information | Génét. Sél. Evol. 1988 20 4 511-516 Note Threshold models with heterogeneous residual variance due to missing information I. MISZTAL D. GIANOLA and Ina HOESCHELE University of Illinois Department of Animal Sciences Urbana IL 61801 USA Warsaw Agricultural University Department of Animal Sciences SGGW-AR Przejazd 4 05-840 Brwinow Poland Virginia Polytechnic Institute and State University Department of Dairy Science Blacksburg VA 24061 USA Summary Threshold model equations are modified to account for unequal variances of residual effects in the underlying scale. Modifications are simple and can be easily incorporated in programs that conduct a threshold model analysis under the usual assumption of homoscedasticity. Key words threshold model sire evaluation heterogeneous variance. Resume Les modèles à seuils à variance résiduelle hétérogène du fait d une information incomplete Les équations relatives au modèle à seuils peuvent être modiíiées afin de prendre en compte des variances résiduelles inégales des effets mesurés sur réchelle sous-jacente. Les modifications à apporter sont simples et peuvent être aisément incorporées dans les programmes effectuant une analyse par modèie à seuil sous 1 hypothèse habituelie d homoscedasticite. Mots clés modèle à seuil evaluation des pères variance hétérogène. I. Introduction Threshold model equations Gianola Foulley 1983 Harville Mee 1984 were originally derived assuming that the residuals of the model for the underlying normal variable have constant variance. This may not be true in general. Also even if the assumption holds there are certain genetic evaluation models where lack of some information leads to heterogeneity of residual variance. For example consider a sire -maternal grandsire model Everett et al. 1979 Quaas et al. 1979 . Here the residual 512 I. MISZTAL D. GIANOLA Ina HOESCHELE variance depends on whether or not the sire or maternal grandsire is identified. If any of these ancestors is not identified its effect is .
