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Daily Tracking Poll Methodology

Monday, November 1, 2004; 5:00 PM

The Washington Post tracking poll will be conducted daily until election day. Results are based on telephone interviews with a randomly selected national sample of adults, including self-identified registered voters and likely voters.

The Post and ABC News collect data jointly but are responsible for developing their own methods to identify likely voters. This may produce slightly different estimates of candidate support. The margin of sampling error is plus or minus 3 percentage points for registered and likely voters, and slightly larger for subsamples. Sampling error is only one of many potential sources of error in this or any other public opinion poll. Interviewing was conducted by TNS of Horsham, Pa.

This tracking poll is based on a rolling three-day sample. About 350 likely voters are polled each day. To update the numbers, a new day's sample of respondents is added to the total sample and the oldest day's sample of respondents is dropped out. The Post uses seven variables to define likely voters, including whether the respondent states they are registered to vote, their intention to vote, past voting history, interest in the presidential campaign, age, whether the respondent is voting for the first time in 2004 and whether the voter knows the location of his or her polling place. These variables produce a sample of likely voters that is largely composed of individuals who regularly vote in presidential elections but does include newly registered as well as other first time voters. In a typical sample, about one in 10 likely voters are self-described first-time voters and one in six are between the ages of 18-29.

The Post adjusts, or "weights," each day's randomly selected samples of adults to match the voting-age population percentages by age, sex, race, and education, as reported by the Census Bureau’s Current Population Survey. The Post also adjusts the percentages of self-identified Democrats and Republicans by partially weighting to bring the percentages of those groups to within three percentage points of their proportion of the electorate, as measured by national exit polls of voters in the last three presidential elections.

10/31: 2,904 likely voters; 3,511 self-identified registered voters Oct. 28-31.

10/30: 2,615 likely voters; 3,165 self-identified registered voters Oct. 27-30.

10/29: 2,347 likely voters; 2,832 self-identified registered voters Oct. 26-29.

10/29: 2,047 likely voters; 2,488 self-identified registered voters Oct. 25-28.

10/28: 1,747 likely voters; 2,145 self-identified registered voters Oct. 24-27.

10/27: 1,709 likely voters; 2,107 self-identified registered voters Oct.23-26.

10/26: 1,666 likely voters; 2,084 self-identified registered voters Oct.22-25.

10/25: 1,631 likely voters; 2,079 self-identified registered voters Oct. 21-24.

10/24: 1,638 likely voters; 2,085 self-identified registered voters Oct. 20-23.

10/23: 1,222 likely voters; 1,575 self-identified registered voters Oct. 20-22.

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