Portrait of the English statistician Karl Pearson (1857- 1936). Pearson studied mathematics at Cambridge and afterwards physics and biology in Germany. In 1884 he became professor of mathematics at University College, London. Pearson's work represents a milestone in 20th century statistics and he was particularly brilliant at applying statistical methods to biological problems. In 1900 he developed the Chi Square test, a criterion to measure the extent to which a theoretical probability distribution fits a set of data.