Results for this survey are based on telephone interviews conducted under the direction of Abt SRBI, Inc., among a nationwide sample of 2,905 adults, 18 years of age or older, from July 31-August 10, 2008 (2,254 respondents were interviewed on a landline telephone, and 651 were interviewed on a cell phone, including 262 who had no landline telephone). Both the landline and cell phone samples were provided by Survey Sampling International.
The combined landline and cell phone data were weighted using demographic weighting parameters derived from the March 2007 Census Bureau’s Current Population Survey, along with an estimate of current patterns of telephone status in the U.S. derived from the 2007 National Health Interview Survey, using an iterative technique that simultaneously balances the distributions of all weighting parameters. The weighting procedure also accounted for the fact that respondents with both landline and cell phones had 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 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 Projects
This survey is a joint effort of the Pew Research Center for the People & the Press and the Pew Forum on Religion & Public Life. Both organizations are sponsored by the Pew Charitable Trusts and are projects of the Pew Research Center, a nonpartisan “fact tank” that provides information on the issues, attitudes and trends shaping America and the world.
The Pew Forum on Religion & Public Life seeks to promote a deeper understanding of issues at the intersection of religion and public affairs. It studies public opinion, demographics and other important aspects of religion and public life in the U.S. and around the world. It also provides a neutral venue for discussions of timely issues through roundtables and briefings.
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. 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 the Center’s current survey results are made available free of charge.
This report is a collaborative product based on the input and analysis of the following individuals:
Pew Forum on Religion & Public Life
Luis Lugo Director
Sandra Stencel Deputy Director
John C. Green Senior Fellow in Religion and American Politics
Gregory Smith Research Fellow
Allison Pond Research Associate
Tracy Miller Editor
Pew Research Center for the People & the Press
Andrew Kohut Director
Scott Keeter Director of Survey Research
Michael Dimock Associate Directors
Kim Parker Senior Researcher
Juliana Menasce Horowitz
Jocelyn Kiley Research Associates
Alec Tyson Research Analysts
James Albrittain Research Assistant