How the poll on independent voters was conducted

How the poll on independent voters was conducted

The data from the AP-GfK polls combines surveys conducted Apr. 7-12, May 7-11 and June 9-14 by GfK Roper Public Affairs & Corporate Communications. The combined dataset is based on landline and cell phone interviews with a nationally representative random sample of 3,047 adults.

For each of the three separate surveys, digits in the phone numbers dialed were generated randomly to reach households with unlisted and listed landline and cell phone numbers.

Interviews were conducted in both English and Spanish.

As is done routinely in surveys, results were weighted, or adjusted, to ensure that responses accurately reflect the population’s makeup by factors such as age, sex, education, and race. In addition, the weighting took into account patterns of phone use — landline only, cell only and both types — by region.

Weighting was performed on the three polls separately.

No more than one time in 20 should chance variations in the combined sample cause the results to vary by more than plus or minus 2.4 percentage points from the answers that would be obtained if all adults in the U.S. were polled.

There are other sources of potential error in polls, including the wording and order of questions.

The questions and results for the three individual polls are available at www.ap-gfkpoll.com.

The exit poll for the November 2008 presidential election was conducted by Edison Media Research and Mitofsky International for The Associated Press and television networks in 300 precincts nationally. The data was based on 17,836 voters, including telephone polling of 2,407 people who voted early, and has a margin of sampling error of plus or minus 1 percentage point.