About the Survey | Pew Research Center

The analysis in this report is based on telephone interviews conducted January 7-11, 2015 among a national sample of 1,504 adults, 18 years of age or older, living in all 50 U.S. states and

the District of Columbia (528 respondents were interviewed on a landline telephone, and 976 were interviewed on a cell phone, including 563 who had no landline telephone). The survey was

conducted by interviewers at Princeton Data Source under the direction of Princeton Survey Research Associates International. A combination of landline and cell phone random digit dial

samples were used; both samples were provided by Survey Sampling International. Interviews were conducted in English and Spanish. Respondents in the landline sample were selected by randomly

asking for the youngest adult male or female who is now at home. Interviews in the cell sample were conducted with the person who answered the phone, if that person was an adult 18 years of

age or older. For detailed information about our survey methodology, see http://pewresearch.org/pewresearch-org/politics/methodology/ The combined landline and cell phone sample are

weighted using an iterative technique that matches gender, age, education, race, Hispanic origin and nativity and region to parameters from the 2013 Census Bureau’s American Community Survey

and population density to parameters from the Decennial Census. The sample also is weighted to match current patterns of telephone status (landline only, cell phone only, or both landline

and cell phone), based on extrapolations from the 2014 National Health Interview Survey. The weighting procedure also accounts for the fact that respondents with both landline and cell

phones have a greater probability of being included in the combined sample and adjusts for household size among respondents with a landline phone. Sampling errors and statistical tests of

significance take into account the effect of weighting. 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.