SIU professor weighs in on methodology of polling - KFVS12 News & Weather Cape Girardeau, Carbondale, Poplar Bluff

SIU professor weighs in on methodology of polling

(Source: KFVS) (Source: KFVS)
CARBONDALE, IL (KFVS) -

President Donald Trump is telling the country not to trust poll data about him, but only if that data casts him in a negative light.

He said those polls are fake and shouldn't be trusted.

This all appears to have been sparked by a series of polls that show between 50 and 60 percent of the nation disapproves of the president's recent travel executive order to ban travel for people from certain countries.

President Trump tweeted about negative polls being fake news, then proceeded to compare recent poll data to other major polls that predicted more people supported Hillary Clinton just before the election.

Southern Illinois University's top political science professor said that comparison is invalid. Not because it's a partisan statement, but because the pre-election polls the president referred to were actually correct.

"[Clinton] didn’t win the election because the election was about the electoral college and everything else, but the popular vote, the nationwide big, costly, well-done polls that are done in the correct way... they had her up by a few percentage points, and that’s what she won the popular vote by. said Tobin Grant, interim department head for SIU's Political Science Department.

"The polls were actually very accurate."

"Poll after poll after poll are all doing the same thing, and finding the same answer, and the reason why that works is that what they're saying is scientifically valid." Grant continued.

He said the opinion polls being done by major news outlets cost a minimum of $50,000 to $100,000 for each poll.

"...so they're spending a lot of money to get a very accurate picture and what they get out of it, when they have an accurate poll, that's their incentive," he said.

Grant said if you're going to discount the polls, before and after the election, you have to look and see if the results were different.

He also pointed out that different news outlets may sample from different groups.

"Fox News polls are usually a representative of registered voters, while ABC's is of everybody, and not just non-citizens, but young people, people who just don't vote and people not registered, so they use that little filter," Grant said.

For those at home wondering what to believe, Grant said there are plenty of polls and if you see really consistent numbers across all of the polls, he said that's something you can usually hold your hat on.

Grant recommends checking the poll's rating on a poll critic website.

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