Survey conducted August 27-October 4, 2015
Most of the analysis in this report is based on telephone interviews conducted August 27-October 4, 2015 among a national sample of 6,004 adults, 18 years of age or older, living in all 50 U.S. states and the District of Columbia (2,113 respondents were interviewed on a landline, and 3,891 were interviewed on a cellphone, including 2,227 who had no landline telephone). The survey was conducted under the direction of Abt SRBI. A combination of landline and cellphone 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 https://www.pewresearch.org/methodology/u-s-survey-research/
Data collection was divided equally into two phases (A and B) with independent samples, non-overlapping interview dates and separate weighting. The questionnaire for each phase contained a core set of measures of political attitudes and values, political engagement and demographic characteristics.
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. The margins of error reported and statistical tests of significance are adjusted to account for the survey’s design effect, a measure of how much efficiency is lost from the weighting procedures.
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:
Survey conducted September 22-27, 2015
Some of the analysis in this report is also based on telephone interviews conducted September 22-27, 2015 among a national sample of 1,502 adults, 18 years of age or older, living in all 50 U.S. states and the District of Columbia (525 respondents were interviewed on a landline telephone, and 977 were interviewed on a cell phone, including 560 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.
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. The margins of error reported and statistical tests of significance are adjusted to account for the survey’s design effect, a measure of how much efficiency is lost from the weighting procedures. 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:
Survey conducted October 16-20, 2015
Additionally, some of the analysis in this report is based on telephone interviews conducted October 16-20, 2015 among a national sample of 1,018 adults, 18 years of age or older, living in the continental United States (510 respondents were interviewed on a landline telephone, and 508 were interviewed on a cell phone, including 329 who had no landline telephone). The survey was conducted under the direction of Social Science Research Solutions (SSRS). A combination of landline and cell phone random digit dial samples were used; both samples were provided by Marketing Systems Group. Interviews were conducted in English and Spanish.
The combined landline and cell phone sample are weighted using an iterative technique that matches gender by age, education, race, Hispanic origin and nativity, marital status and region by gender to parameters from the March 2014 supplement of the U.S. Census Bureau’s Current Population 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 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, adjusts for the number of landlines and cellphones the respondent answers and adjusts for household size among respondents with a landline phone. The margins of error reported and statistical tests of significance are adjusted to account for the survey’s design effect, a measure of how much efficiency is lost from the weighting procedures.
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.
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