EXAMPLE 4 Public opinion polls

Polls such as those conducted by Gallup and many news organizations ask people’s opinions on a variety of issues. The variables measured are responses to questions about public issues. Though most noticed at election time, these polls are conducted on a regular basis throughout the year. For a typical opinion poll:

Population: U.S. residents 18 years of age and over. Noncitizens and even illegal immigrants are included.

Sample: Between 1000 and 1500 people interviewed by telephone.