Pew Research Center January – February 2015 Survey
This report is based on telephone surveys in the United States and Japan conducted under the direction of Princeton Survey Research Associates International.
In the U.S., interviews were conducted February 12-15, 2015 among a national sample of 1,000 adults, 18 years of age or older, living in the continental United States (500 respondents were interviewed on a landline telephone, and 500 were interviewed on a cell phone, including 310 without a landline phone – roughly 95% of U.S. households). Interviews were done in English and Spanish. Statistical results are weighted to account for probability of being included in the sample and to correct known demographic discrepancies. The margin of sampling error for the complete set of weighted data is ± 3.6 percentage points.
In Japan, interviews were conducted January 30 to February 12, 2015 among a national sample of 1,000 persons, 18 years of age or older, living in Japan. All interviews were conducted on a landline telephone using Random Digit Dialing (RDD) (roughly 79% of all Japanese households). Interviews were exclusively conducted in Japanese. Statistical results are weighted to correct known demographic discrepancies. The margin of sampling error for the complete set of weighted data is ± 3.2 percentage points.
The margin of sampling error reported is based on all interviews conducted in a country. The margin of error takes into account the design effect due to weighting. For results based on the full sample in a given country, one can say with 95% confidence that the error attributable to sampling and other random effects is plus or minus the margin of error. The margin of error is larger for results based on subgroups in the survey. Sample sizes and sampling errors for 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.
