Results for this report are based on telephone interviews among a nationwide sample of 1,003 adults, 18 years of age or older, conducted Feb. 28-March 2, 2008 under the direction of ORC (Opinion Research Corporation). For results based on the total sample, one can say with 95% confidence that the error attributable to sampling is plus or minus 3.5 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, and that results based on subgroups will have larger margins of error.