The Gallup Polls were inaugurated in 1935, with the founding of the American Institute of Public Opinion, which today has offices in Princeton, New Jersey and New York City. The organization originatesquestions, gathers answers and then organizes the results.

      The Audience Research Institute, Inc., is an associated organization, founded by Gallup in 1939, primarily to evaluate the public reaction to movie titles, casts and stories. Besides the regular polls, there are four a week, the AIPO from time to time undertakes special surveys on subjects as reader preferences for the selections of the Book-of-the-month club, the pulling power of titles for Bantam books, and the popularity of radio stars. Affiliates of the AIPO conduct Gallup polls in eleven foreign countries. In 1948, Time estimated the annual operating budget of the enterprises at about $750,000 yearly.

      The stated purpose of the American Institute of Public Opinion is "to impartially measure and report public opinion on political and social issues of the day without regard to the rightness or wisdom of the views expressed. " Behind Gallup's claims that his polls are a true representation of the opinions of the whole nation is a theory based on a study of "probable error due to sample size " made by a Professor Theodore Brown of Harvard.

      Gallup illustrated the theory by saying that if random samples of 2,500 beans were taken from a barrel of white and black beans, in only three out of 1,000 samples would the proportion of the black to white beans vary from the proportion in the barrel itself.

      For a good measure, he based his polls on 3,000 samples. This was the first time the concept of screening respondents was used. An innovation in poll-taking is what the institute calls the "quintamensional plan of question design" for complex issues, by which a series of preliminary questions were asked of the person polled in order to establish his competency to form an opinion on the issue.
     Here is a link to Gallup Organization's Gallup Poll.