Results for this survey are based on telephone interviews conducted under the direction of Princeton Survey Research Associates among a nationwide sample of 1,503 adults, 18 years of age or older, from January 7-11, 2009 (1,128 respondents were interviewed on a landline telephone, and 375 were interviewed on a cell phone, including 112 who had no landline telephone). Both the landline and cell phone samples were provided by Survey Sampling International.
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 2007 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 2007 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 sample.
The following table shows the error attributable to sampling that would be expected at the 95% level of confidence for different gr oups in the survey:
| Group | Sample Size | Plus or minus… |
| Total sample | 1,503 | 3.0 percentage points |
| Form 1 sample | 769 | 4.0 percentage points |
| Form 2 sample | 734 | 4.0 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.
ABOUT THE CENTER
The Pew Research Center for the People & the Press is an independent opinion research group that studies attitudes toward the press, politics and public policy issues. We are sponsored by The Pew Charitable Trusts and are one of seven projects that make up the Pew Research Center, a nonpartisan “fact tank” that provides information on the issues, attitudes and trends shaping America and the world.
The Center’s purpose is to serve as a forum for ideas on the media and public policy through public opinion research. In this role it serves as an important information resource for political leaders, journalists, scholars, and public interest organizations. All of our current survey results are made available free of charge.
All of the Center’s research and reports are collaborative products based on the input and analysis of the entire Center staff consisting of:
Andrew Kohut, Director Scott Keeter, Director of Survey Research Carroll Doherty and Michael Dimock, Associate Directors Michael Remez, Senior Writer Juliana Menasce Horowitz, Robert Suls, Shawn Neidorf, Leah Christian, Jocelyn Kiley and Neha Sahgal, Research Associates Kathleen Holzwart and Alec Tyson, Research Analysts
