Changes

The sample had to be a ''valid'' representation of the population, which means that each person in the target population has a known chance of being sampled.<ref> In unweighted samples, each person has an equal chance. If people have a known but unequal chance, they are weighted to make the chances appear equal.</ref>  Unscientific public opinion polls, made by collecting information from a haphazard sample, date from the '''straw polls''' in American elections in the 1820s. As soon as modern statistical sampling theory was invented around 1930, [[George Gallup]] and other advertisers started created nationwide public opinion polls, using about 1500 cases. The American public became fascinated with polls and they spread to many democratic countries by 1940. Totalitarian countries did not allow them.

The sample had to be a ''valid'' representation of the population, which means that each person in the target population has a known chance of being sampled.<ref> In unweighted samples, each person has an equal chance. If people have a known but unequal chance, they are weighted to make the chances appear equal.</ref>  Unscientific public opinion polls, made by collecting information from a haphazard sample, date from the '''straw polls''' in American elections in the 1820s. As soon as modern statistical sampling theory was invented around 1930, [[George Gallup]] and other advertisers started created nationwide public opinion polls, using about 1500 cases. The American public became fascinated with polls and they spread to many democratic countries by 1940. Totalitarian countries did not allow them.

==History of Opinion Polls==

==History of Polling==

The first known example of an opinion poll was a local straw vote conducted by a newspaper ''The Harrisburg Pennsylvanian'' in 1824; it showed [[Andrew Jackson]] leading [[John Quincy Adams]] by 335 votes to 169 in the contest for the presidency. Such straw votes&mdash;unweighted and unscientific&mdash; gradually became more popular; but they remained local, usually city-wide phenomena. In 1916, the large-circulation U.S. magazine ''[[Literary Digest]]'' embarked on a national survey (partly as a circulation-raising exercise) and correctly predicted Woodrow Wilson's election as president. Mailing out millions of postcards and simply counting the returns, the ''Digest'' correctly called the following four presidential elections.

The first known example of an opinion poll was a local straw vote conducted by a newspaper ''The Harrisburg Pennsylvanian'' in 1824; it showed [[Andrew Jackson]] leading [[John Quincy Adams]] by 335 votes to 169 in the contest for the presidency. Such straw votes&mdash;unweighted and unscientific&mdash; gradually became more popular; but they remained local, usually city-wide phenomena. In 1916, the large-circulation U.S. magazine ''[[Literary Digest]]'' embarked on a national survey (partly as a circulation-raising exercise) and correctly predicted Woodrow Wilson's election as president. Mailing out millions of postcards and simply counting the returns, the ''Digest'' correctly called the following four presidential elections.