Most of the analysis in this report is based on telephone interviews conducted under the direction of Princeton Survey Research Associates International among a national sample of 2,505 adults living in the continental United States, 18 years of age or older, from March 11-21, 2010 (1,677 respondents were interviewed on a landline telephone, and 828 were interviewed on a cell phone, including 301 who had no landline telephone). Both the landline and cell phone samples were provided by Survey Sampling International. Interviews were conducted in English and Spanish. For detailed information about our survey methodology, see the methodology section of our website at: https://www.pewresearch.org/politics/methodology/.
The combined landline and cell phone sample are weighted using an iterative technique that matches gender, age, education, race/ethnicity, region, and population density to parameters from the March 2009 Census Bureau’s Current Population Survey. The sample is also weighted to match current patterns of telephone status and relative usage of landline and cell phones (for those with both), based on extrapolations from the 2009 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 within the landline sample. Sampling errors and statistical tests of significance take into account the effect of weighting.
The following table shows the error attributable to sampling that would be expected at the 95% level of confidence for different groups in the survey:
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.
About the additional surveys
In addition to the main survey described above, this report is supplemented with three additional surveys. Results for these three surveys are based on landline and cell phone interviews conducted under the direction of Princeton Survey Research Associates International among nationwide samples of adults, 18 years of age or older, living in the continental United States. The landline and cell phone samples were provided by Survey Sampling International. Interviews were conducted in English.
The first survey was conducted March 18-21, 2010 among a sample of 1,002 adults (671 respondents were interviewed on a landline telephone, and 331 were interviewed on a cell phone, including 143 who had no landline telephone). The second survey was conducted April 1-5, 2010 among a sample of 1,001 adults (670 respondents were interviewed on a landline telephone, and 331 were interviewed on a cell phone, including 120 who had no landline telephone). The third survey was conducted April 8-11, 2010 among a sample of 1,001 adults (670 respondents were interviewed on a landline telephone, and 331 were interviewed on a cell phone, including 124 who had no landline telephone).
The combined landline and cell phone sample are weighted using an iterative technique that matches gender, age, education, race/ethnicity, region, and population density to parameters from the March 2009 Census Bureau’s Current Population Survey. The sample is also weighted to match current patterns of telephone status based on extrapolations from the 2009 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 within the landline sample. Sampling errors and statistical tests of significance take into account the effect of weighting.
The error attributable to sampling that would be expected at the 95% level of confidence for the total sample in each survey is plus or minus 4 percentage points. 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.
