The Associated Press-GfK poll on the health care overhaul was conducted by GfK Public Affairs and Corporate Communications May 16-19. It is based on online interviews of 1,354 adults who are members of GfK's nationally representative KnowledgePanel, including 310 adults who have never been married.
The original sample was drawn from a panel of respondents recruited via phone or mail survey methods. GfK provides Internet 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, online surveys using KnowledgePanel are nationally representative.
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, race, education and phone usage. In addition, adjustments were made before weighting to account for the oversample of never-married adults.
No more than 1 time in 20 should chance variations in the sample cause the results to vary by more than plus or minus 3 percentage points from the answers that would be obtained if all adults in the U.S. were polled. The poll had a cooperation rate of 44 percent.
There are other sources of potential error in polls, including the wording and order of questions.
The questions and results are available at http://www.ap-gfkpoll.com .