The margin of sampling error is typically calculated with a statistical formula. But the true margin of error for a poll can be twice as large as reported, research has shown.

As Americans await election results, many are looking to the polls for clues. From the margins of error to methodology, here’s what to know about presidential polls.

As the director of the Quinnipiac University Poll, which has been taking the pulse of the public on policy issues and elections for the past 30 years, I’ve noted that people have been paying ...