The AP-Yahoo News Poll is a unique study that is tracking the moods and opinions of a group of people throughout the presidential election campaign. The fifth wave of this study included re-interviews between June 13-23 with 1,759 people who originally were interviewed in November or early December. The extensive national survey was conducted by Knowledge Networks of Menlo Park, California, under the direction and supervision of AP's polling unit.
The interviews were conducted online. The original sample was drawn from a panel of respondents Knowledge Networks recruited via random sampling of landline telephone households with listed and unlisted numbers. The company provides Web access to panel recruits who don't already have it. 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, and education.
No more than one time in 20 should chance variations in the sample cause results to vary more than plus or minus 2.3 percentage points from the answers that would have been obtained if all adults in the U.S. were surveyed. The sampling error margin is plus or minus 3.4 percentage points for the subsample of 844 Democrats and those who lean toward the Democratic Party, 3.9 percentage points for the subsample of 637 Republicans and those who lean toward the Republican Party.
There are other, potentially greater, sources of variability in surveys, including the wording and order of the questions.
http://news.yahoo.com/polls
http://surveys.ap.org
