Qué·te·let \kā-tə-lā\ Lambert Adolphe Jacques (1796–1874), Belgian astronomer and statistician. Quételet is remembered chiefly for his application of statistics and probability theory to social phenomena. As an astronomer he is credited with founding in 1828 Brussels's Royal Observatory and developing methods for the simultaneous observation of astronomical, meteorological, and geodetic phenomena from various European locations. As a statistician he collected and analyzed statistics on crime, mortality, and other phenomena for the Dutch and Belgian governments. In 1835 he published his treatise Sur l'homme in which he first presented his conception of the “average man,” using it as the central value about which measurements of various human traits are distributed according to the normal curve. He used stature, weight, complexion and other physical traits as criteria for determining the “average man” in any given race or population. Quételet's “average man” became a catch phrase in 19th-century discussions on social science.