Results for the early October 2004 political survey are based on telephone interviews conducted under the direction of Princeton Survey Research Associates International among a nationwide sample of 1,233 adults, 18 years of age or older, during the period October 1-3, 2004. For results based on registered voters (N=1,002) one can say with 95% confidence that the error attributable to sampling is plus or minus 3.5 percentage points.
Results from the September 2004 political survey are based on telephone interviews among a nationwide sample of 2,003 adults, 18 years of age or older, during the period September 8-13, 2004. The error attributable to sampling is plus or minus 2.5 percentage points. For results based on registered voters (N=1,580) the sampling error is plus or minus 3 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.
