The Associated Press-NORC Center for Public Affairs Research poll on drugs and substance abuse was conducted by NORC Feb. 11-14. It is based on online and telephone interviews of 1,042 adults who are members of NORC's nationally representative AmeriSpeak panel.
The original sample was drawn from respondents selected randomly from NORC's National Frame based on address-based sampling and recruited by mail, email, telephone and face-to-face interviews.
NORC interviews participants over the phone if they don't have Internet access. With a probability basis and coverage of people who can't access the Internet, surveys using AmeriSpeak are nationally representative.
Interviews were conducted in English.
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, region and phone use.
No more than 1 time in 20 should chance variations in the sample cause the results to vary by more than plus or minus 3.9 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 are available at http://http://www.apnorc.org