The national survey was conducted online by GfK of Palo Alto, Calif., under the direction and supervision of the AP's polling unit.
The original sample was drawn from a panel of respondents GfK recruited via phone or mail survey methods. 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, GfK's online surveys using KnowledgePanel 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 3.8 percentage points from the answers that would be obtained if all adults 18-49 in the U.S. were polled. The margin of sampling error for women ages 18-49 who have never married and have children or are pregnant is plus or minus 8.9 percentage points.
There are other sources of potential error in polls, including the wording and order of questions.
The questions and results are available at http://surveys.ap.org .