Midparent

In human genetics the midparent value of a trait is defined as the average of the trait value of the father and a scaled version of that of the mother. This value can be used in a study to analyze the data set without heeding sex effects. Studying quantitative traits in heritability studies may be complicated by sex differences observed for the trait.

Well-known examples include studies of humans' height, whose midparent value h_mp is given by:¹

h_{mp}={\frac {h_{f}+(1.08\times h_{m})}{2}}

where h_f is the father's height, and h_m the mother's.

The coefficient 1.08 serves as a scaling factor. After the 1.08 scaling, the mean of the mother's height is the same as that of the father's, and the variance is closer to the father's; in this way, sex difference can be ignored.

References

Vogel, Friedrich; Motulsky, Arno G. (1997). "Formal Genetics of Humans: Multifactorial Inheritance and Common Diseases". Human Genetics. Problems and Approaches. p. 207. doi:10.1007/978-3-662-03356-2_7. ISBN 978-3-662-03356-2.

[1] Vogel, Friedrich; Motulsky, Arno G. (1997). "Formal Genetics of Humans: Multifactorial Inheritance and Common Diseases". Human Genetics. Problems and Approaches. p. 207. doi:10.1007/978-3-662-03356-2_7. ISBN 978-3-662-03356-2.

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