Understanding polls: What to know about margin of error, methods and more

As Americans await election results, many are looking to the polls for answers. 

JUMP TO: MARGIN OF ERROR l PHONE/DIGITAL l OUTLIER POLLS

Dr. Andy Smith, from the University of New Hampshire Survey Center, joined LiveNOW from FOX on Election Day with tips for deciphering the pollsand how to better understand them. 

What is margin of error?

Margin of error describes how close a survey result can reasonably be, relative to the true representative of the entire population. In other words, even the purest random sampling of surveyors won’t be an exact match of the entire American population. 

• MORE: Track live results here on election night

Calculating the margin of error works through a complicated mathematical theory known as the central limit theorem, Smith said. But he gave some tips for understanding it more easily. 

He said the biggest confusion about sampling error is that people think it applies to the percentage gap between the candidates, which isn’t the case. 

Who is currently leading in the polls?

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"What you have to do is apply a margin of sampling error to both estimates," he said. "So Donald Trump at 46%, in this example (with a 3% error of margin), he might be up to 49%; he might be as low as 43%. Harris at 50%, could be as low as 47% or as high as 53%."

"You really have to about double the margin of sampling error if you want to understand if the gap between those two candidates is statistically significant," he added.

Phone vs. digital polls

"The polling industry is going through what I would call a paradigm shift, where we're moving from the types of methods that worked 30, 40 years ago and don't really work anymore," Smith said. 

He said response rates for phone interviews have significantly declined in recent years, to the point where he said only about 5% of people who get contacted for telephone surveys actually complete them. 

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"This results in very, very expensive telephone surveys and, (as we saw) in 2016, inaccurate telephone surveys," he said. 

He said more surveys are being conducted digitally this election, but that several different methodologies for digital methods also exist.

"We're going to see after this election quite a bit of research to understand which one of the methodologies that were used actually performed best, and use that knowledge that we got going forward," he said. 

"I'm very cautious in saying one poll is better than another poll right now because frankly, we just don't know. We are in the middle of this development of our best practices and we're not at the end of that yet."

Outlier polls

Every election cycle, a handful of polls publish shocking results that drum up significant attention. 

Most recently was the highly anticipated poll from J. Ann Selzer, the "gold standard" pollster in Iowa, showing Kamala Harris beating Donald Trump by 3 points in the Hawkeye State.

So, how do some poll results vary so differently? 

Smith says it could have to do with how the survey was conducted, or that an unusual sampling group was used that may have excluded a certain demographic.