The correlation between relatives on the supposition of Mendelian inheritance.

"Fisher put forward a genetics conceptual model that shows that continuous variation amongst phenotypic traits could be the result of Mendelian inheritance. The paper also contains the first use of the statistical term variance" ( Wikipedia article on The Correlation between Relatives on the Supposition of Mendelian Inheritance, accessed 03-2017).

Fisher reconciled Mendelian genetics with the biometric observations of Karl Pearson and Francis Galton. Reprinted, with extended commentary in Eugen. Lab. Mem., Univ. Coll. Lond., 1966, 41.