How exit polls work and what they tell us on election night

CNN
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What are exit polls? These are a series of surveys that ask voters who they voted for, as well as additional questions about their political opinions, the factors they considered when voting, and their own background in general.

This helps us better understand who voted, how different groups of people voted, and where they stand on some of the campaign's biggest issues.

The earliest results of this year's election polls will be announced after 5:00 p.m. ET on Election Day. Data that could characterize the outcome of a race will not be announced until after polls close.

Election polls are conducted by Edison Research for the National Election Pool on behalf of a consortium of media companies: CNN, ABC, CBS and NBC. They get their name because interviewers are stationed at about 500 polling stations across the country on Election Day, where they conduct surveys with a random sample of voters who have just cast their ballots. The polling places themselves were selected through random sampling, meaning the resulting interviews should be representative of Election Day voters statewide or nationally. Interviewers call back several times throughout the day to report their findings – meaning the initial numbers are likely to change as more data comes in.

But polling doesn't start on Election Day: It's also designed to reflect the views of the millions of Americans who voted before November 5th. In some states, interviewers are also stationed at about 100 early in-person voting sites.

And the results also include voters who voted early by mail or postal vote. This portion of the electorate is reached through more traditional preelection polls, conducted by calling, emailing and sending text messages to people selected from lists of all registered voters.

In addition to national election polls, there are also election polls conducted in specific states that focus on important, competitive presidential or recall elections. This year, those states include Arizona, Georgia, Florida, Michigan, Nevada, North Carolina, Ohio, Pennsylvania, Texas and Wisconsin.

In-person exit surveys are conducted using paper surveys that respondents complete themselves; People reached by email or text answer questions online, while people reached by phone answer questions from a live interviewer. Each exit survey contains approximately 20 to 25 questions and is designed to take approximately five minutes to complete. Each voter's answers are anonymous.

Ultimately, exit polls will include interviews with tens of thousands of voters. This scope makes them a powerful tool for understanding the demographic profile and political views of voters in this year's election. And their results are ultimately compared to the ultimate benchmark: the results of the elections themselves.

However, exit polls are still polls with margins of error – meaning they are most useful when treated as estimates rather than precise measurements. This is particularly true for the earliest election results, which have not yet been adjusted to the final election results.

CNN's Jennifer Agiesta contributed to this report.