Results for the national survey are based on telephone interviews conducted under the direction of Schulman, Ronca, & Bucuvalas, Inc. among a nationwide sample of 1,399 adults, 18 years of age or older, from November 20-26, 2007. For results based on the total sample, one can say with 95% confidence that the error attributable to sampling is plus or minus 3 percentage points. For results based on likely Democratic or Republican primary voters (N=915), the error attributable to sampling is plus or minus 3.5 percentage points.
Results for the state surveys are based on telephone interviews with a sample of 5,462 adults living in Iowa, New Hampshire, and South Carolina, conducted by Princeton Data Source, LLC under the direction of Princeton Survey Research International, from November 7-25, 2007.
The Iowa survey interviewed a total of 2,111 registered voters, including 724 who say they will definitely or probably attend either the Democratic or Republican caucuses. The margin of error for these likely caucus voters is +-4%.
The New Hampshire survey interviewed a total of 1,300 registered voters, including 1,040 who plan to vote in either the Democratic or Republican primaries. The margin of error for these likely primary voters is +-3.5%.
The South Carolina survey interviewed a total of 1,200 registered voters, including 841 who plan to vote in either the Democratic or Republican primaries. The margin of error for these likely primary voters is +-4%.
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.
