[Analysis of phenotypical correlations between qualitative traits. II. Evaluation of the contribution of the nominal factor to variations in susceptibility to multifactorial diseases].

A method for the evaluation of the coefficient of determination which permits to estimate the contribution of the nominal factor (X) into the variability of multifactorial trait (Y) in the traditional terms of variance is proposed. To construct the coefficient of determination D the data are needed on the incidence of multifactorial trait Y in general population and in subpopulations with given i-th alternatives of X, as well as the frequencies of i-th alternatives of X in both the general population and among the Y bearing persons. The expressions for the calculation of standard errors of D are given. The coefficient of determination can be used in genetic analysis of association between genetic markers, as well as other Mendelian traits, and multifactorial diseases.