A man of wide-ranging interests, Karl Pearson became the father of statistics by an indirect route that led him from mathematics to other disciplines and back again. Among the innovations associated with his establishment of the discipline was his formulation of the concept of the "standard deviation."
Born in London on March 27, 1857, to William, a lawyer, and Fanny Smith Pearson, the future mathematician was a sickly child. His health forced him to conduct part of his early education at home, but at age 17 he went to Cambridge, and followed this with studies in a wide array of subjects at King's College. These subjects included philosophy, religion, literature, and, mathematics, his major, in which he graduated with honors in 1879.
Over the coming years, Pearson traveled throughout Germany, became a socialist, and in 1884 took a position as Goldsmid Professor of Applied Mathematics and Mechanics at University College in London. In 1890 he married Maria Sharpe, with whom he had three children—Egon, Sigrid, and Helga.
Intrigued by Natural Inheritance, a study of heredity by Francis Galton (1822-1911), Pearson reasoned that there must be some mathematical means of testing the correlation between two phenomena. Numbers would show clearly whether the apparent correlation resulted from mere chance, or from a consistent factor. From the beginning, he understood this pursuit primarily in terms of applied rather than pure mathematics, instantly grasping the possible applications of statistical theory for a wide array of disciplines.
It so happened that during this period Pearson met W. F. R. Weldon, a professor of zoology who spurred him on to develop statistical methods for application to the study of heredity and evolution. In the course of these studies, Pearson established the idea of a standard deviation. Standard deviation is a measure of the variance within a sample or population that is based on the average distance from the mean score to any score within the set, and makes it possible to predict the average variance within a set.
In 1901 Pearson founded the journal Biometrika for the publication of studies on statistics. A decade later, he became Galton Professor of Eugenics (the study of genetic factors as a means of preventing disease and other physical impairments), as well as director of a new department of applied statistics at University College. His staff served the British war effort in World War I, providing valuable calculations, and in 1925 he established the journal Annals of Eugenics. He published some 300 works in the course of his career.
Pearson's first wife died in 1928, and he remarried to Margaret V. Child, who also taught at University College, the following year. In 1933, at age 77, he retired, and on April 27, 1936, he died.