The PSRAI September 2014 Omnibus Weeks 2 and 3 obtained telephone interviews with a nationally representative sample of 2,003 adults living in the continental United States. Telephone interviews were conducted by landline (1,002) and cellphone (1,001, including 594 without a landline phone). The survey was conducted by Princeton Survey Research Associates International (PSRAI). Interviews were done in English and Spanish by Princeton Data Source from Sept. 11 to 14, 2014, and Sept. 18 to 21, 2014. Statistical results are weighted to correct known demographic discrepancies. The margin of sampling error for the complete set of weighted data is plus or minus 2.5 percentage points.

The following table shows the unweighted sample sizes and the error attributable to sampling that would be expected at the 95% level of confidence for different groups in the survey:

Sample sizes and sampling errors for other subgroups are available upon request.

In addition to sampling error, one should bear in mind that question wording and practical difficulties in conducting surveys can introduce error or bias into the findings of opinion polls.