The variances of the means and the variance of the slope of the line of relation of a linear, composite, bivariate distribution, in which the variances and correlation coefficient of the component populations remain constant, are analogous to the corresponding variances of a linear regression line. The variances of the means are respectively,, and the variance of the slope of the line of relation is,whereare the variances of the component populations,is the vertical variance of the composite distribution around the line of relation,Nis the total number of measures, andis the variance of the composite distribution around theY-axis.