The survey in Japan is part of the larger Spring 2011 Pew Global Attitudes survey conducted in 22 countries and the Palestinian territories under the direction of Princeton Survey Research Associates International.
Results for the survey in Japan are based on 700 landline telephone interviews of adults conducted April 8 to April 27. Between May 13 and May 24, 2011, 601 respondents were re-contacted and asked about the effects of the earthquake and tsunami. The survey uses a Random Digit Dial (RDD) probability sample, representative of all landline telephone households stratified by region and population size, excluding 5% of the population living in areas most affected by the earthquake. Those in cell phone only households (less than 5%) were excluded from the survey. All interviews were conducted in Japanese.
The margin of sampling error is ±4.5 percentage points. For the results based on the full sample, one can say with 95% confidence that the error attributable to sampling and other random effects is plus or minus the margin of error. 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.