Exit polls, like any other survey, are subject to sampling errors. Before news organizations report any exit poll results or make projections, therefore, they compare results to pre-election polls, past precinct voting history, and have statisticians and political experts carefully review the data.
After the polls close the exit poll results are weighted using the actual vote count to make the data more accurate. Even projections that are made without any actual vote data are not based solely on the results of exit polls.
How do exit polls account for the people who vote early or by mail?
In the 2008 election, nearly one third of Americans voted before Election Day, using some form of absentee or early voting. Capturing information about these voters is challenging, but it is critical to report accurate information about all voters.
In states with high numbers of absentee/early voters, telephone polls are conducted to reach those voters. Data from these telephone polls are combined with the exit poll data to provide a complete portrait of all voters. When will exit poll results be reported?
On Election Day, there is a strict quarantine on any news coming from the early waves of exit poll data until 5:00 p.m. ET. By about 5:45 p.m., some initial demographic information about voter turnout will be available on ABCNews.com.
However, no winners will be projected until polls are closed, so announcements come on a state-by-state basis as individual state polls close. Information will be constantly updated throughout the evening on ABCNews.com and on all ABC News programs.
For more information about the history of exit polls, click here.