The media believability report draws on a series of surveys conducted since 1985. The project was initiated by the Times Mirror Center for the People & the Press and continued by the Pew Research Center for the People & the Press since 1996. All believability surveys have been conducted by telephone. Since 2010, cell phone interviewing has been included. All interviews have been conducted in English. The analysis in this report is based primarily on surveys conducted between 2002 and 2012.
The current survey is based on telephone interviews conducted July 19-22, 2012 among a national sample of 1,001 adults 18 years of age or older living in the continental United States (600 respondents were interviewed on a landline telephone, and 401 were interviewed on a cell phone, including 191 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. 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/politics/methodology/.
The combined landline and cell phone sample are weighted using an iterative technique that matches gender, age, education, race, Hispanic origin and region to parameters from the March 2011 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, based on extrapolations from the 2011 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.
With a 95% level of confidence, the margin of error for the total sample of 1,001 is plus-or-minus 3.6 percentage points. Analysis in this report was based on those who could rate each news organization. That number ranged from 796, with a margin of error of plus or minus 4.0 points, to 947, with a margin of error of 3.7 points.
The sample included 239 Republicans, 286 Democrats and 384 independents. Margins of error are 7.4 points, 6.8 points and 5.8 points, respectively. Not all partisans offered ratings of all news organizations. As few as 183 Republicans and as many as 230 Republicans rated the various news outlets, with margins of error ranging from 7.5 to 8.4 percentage points. As few as 222 Democrats and as many as 272 Democrats rated the news outlets, with margins of error from 6.9 to 7.7 percentage points. Among independents, as few as 314 and as many as 363 rated the news outlets, producing margins of error of 6.0 to 6.4 percentage points.
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.
