The Associated Press-Knowledge Networks poll on NFL football was conducted Jan. 21-26, 2011 and is based on 1,125 interviews, including 482 NFL fans.
The national survey was conducted online by Knowledge Networks of Menlo Park, Calif., under the direction and supervision of AP's polling unit.
Knowledge Networks initially contacted people using traditional telephone and mail polling methods and followed with an online interview. People chosen for the study who had no Internet access were given it for free. With a probability basis and coverage of people who otherwise couldn't access the Internet, the Knowledge Networks online surveys are nationally representative.
Results were weighted, or adjusted, to reflect the adult population by demographic factors such as age, sex, region, race, and education.
No more than one time in 20 should chance variations in the sample cause the results to vary by more than plus or minus 3.6 percentage points from the answers that would be obtained if all adults in the U.S. were polled. The margin of sampling error for NFL fans is plus or minus 5.5 percentage points.
There are other, potentially greater, sources of variability in surveys, including the wording and order of the questions.
The questions and results for this poll are available at http://surveys.ap.org.