sentences:  Joseph Berkson
  
  Joseph Berkson (born New York City 14 May 1899 – died 12 September 1982) was trained as a physicist (BSc 1920 College of City of New York, M.A., 1922, Columbia), physician (M.D., 1927, Johns Hopkins), and statistician (Dr.Sc., 1928, Johns Hopkins)..He is best known for having identified a source of bias in observational studies caused by selection effects known as Berkson's paradox
  
  In 1950, as Head (1934–1964) of the Division of Biometry and Medical Statistics of the Mayo Clinic, Rochester, Minnesota, Berkson wrote a key paper entitled "Are there two regressions?