A de Finetti diagram can be used to graph the genotype frequencies of populations, where there are two alleles and the population is diploid. It is based on an equilateral triangle, and the theorem that from any point within the triangle, the sum of the length of the three lines from that point that are perpendicular to the sides of the triangle is equal. This length is set to be 1. The de Finetti diagram is named after the Italian stastistician Bruno de Finetti (1906 — 1985), who was the first to use it to represent genotype frequencies.
