To conduct polls, CNN partners with world-renowned market research firms and consulting agencies, as well as affiliate news agencies. CNN's primary partners and affiliates are Gallup Inc., Yankelovich Inc., USA Today and Time Magazine.
CNN works with its partners and affiliates to formulate objective questions. These questions are often vetted and improved upon by interviewing a small sample of randomly selected people. Once a polling questionnaire has been approved, CNN entrusts Gallup Inc. and Yankelovich Inc. to interview respondents. Interviewees are selected by a computer that dials telephone numbers at random to ensure that the majority of Americans are equally likely to be called. The majority of polls are conducted by interviewing 600-800 people aged 18 or older.
After the poll is conducted, it goes through a process called weighing, in which the pool of respondents is compared to the latest Census Bureau figures to determine whether or not it is an accurate representation of the American population. If the weighing process reveals that the pool of respondents is not representative of the population at large, a small mathematical correction, or weight, is applied. CNN also cites polls conducted by competing media outlets if they are conducted according to the same standards.