Results for the survey are based on telephone interviews conducted under the direction of Princeton Survey Research Associates International among a nationwide sample of 1,800 adults, 18 years of age or older, during the period May 3-9, 2004. Based on the total sample, one can say with 95% confidence that the error attributable to sampling and other random effects is plus or minus 2.5 percentage points. For results based on either Form 1 (N=904) or Form 2 (N=897), the sampling error is plus or minus 3.5 percentage points.
For results based on Registered Voters (N=1465), the sampling error is plus or minus 3 percentage points. For results based on either Form 1 registered voters (N=730) or Form 2 registered voters (N=735), the sampling error is plus or minus 4 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.