George Gallup developed a system of accurate polling, including four principles. What are they?

Gallup's career as a teacher began after he received a bachelor's degree and stayed to teach journalism and psychology from 1923 to 1929 at his alma mater, the University of Iowa. He then moved to Drake University at Des Moines, Iowa, where he served as head of the Department of Journalism until 1931. In that year he moved to Northwestern University, Evanston, Illinois, as professor of journalism and advertising. The next year he moved to New York City to join the advertising agency of Young and Rubicam as director of research and then as vice-president from 1937 to 1947. From 1933 to 1937 he was also professor of journalism at Columbia University, but he had to give up this position shortly after he formed his own polling company, the American Institute of Public Opinion (Gallup Poll), in 1935, where he concentrated on attitude research. He was also the founder (1939) and president of the Audience Research Institute. Other positions were: chief executive officer and chairman of the board of Gallup Organization, Inc., and president of Public Opinion Surveys, Inc., and of Gallup International Research Institutes, Inc., which had 35 affiliates doing research in over 70 foreign countries.

Apart from these business positions Gallup was active in professional and public service groups. He was president of the International Association of Public Opinion Institutes, 1947-1984, and of the National Municipal League, 1953-1956, and chair of the All-America Cities Award Committee, a jury which selects All-America cities on the basis of intelligent and effective citizen activity. He founded Quill and Scroll, an international honor society for high school journalists, and served as chair of its board of trustees. Gallup continued in nearly all of these offices until his death of heart failure on July 27, 1984, in Tschingel, Switzerland.