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A Lesson On Polls


An ABC News poll released Sunday shows Hillary Clinton has a double-digit lead over Donald Trump. But that doesn’t guarantee those results will be duplicated on Election Day.

On Think, Krys Boyd talked with polling expert Harold Clarke about how polling data is collected - and how we should interpret results

The KERA Interview

Harold Clarke on: 

… how polls can be wrong:

“I think especially in this election cycle, where’s there been so much animosity and so much mud throwing going back and forth between the presidential candidates and their surrogates, that we may well have shy voters, particularly shy Trump voters. And this is something that’s been commented on and researched in the U.K. over the past 30 years when in the 1992 general election just a week before the election all the polls where saying that Labour would win a majority. And indeed what happened was a narrow majority for the Conservatives. This set off this big round of research and commentary about the so called shy Tory voter. Well, you’re now seeing in this country discussion of shy Trumpsters.”

… how polls differ from one another:

“Methodologies can be quite different. For example some polling companies still pride themselves on using telephone polls. They think that’s the best way of doing it because they think, perhaps naively, that this is the best way to approximate a random sample, which is sort of the gold standard of sampling. Whereas other companies, for example YouGov, the Internet survey company ...  uses Internet polls. That involves some additional what we call filters, and some different kinds of adjustments. So they can be very different in their methodologies. Not just in mode, but then in terms of how they actually treat the data.”

… who will win the election:

“I think Hillary is going to win. … If you go with the science then you say, ‘OK, this is going to be a victory for Hillary Clinton.’ However there are a couple of caveats that you need to think about. No. 1 is that the polls right now are highly variable. We had an ABC poll out this morning with Hillary 12 points ahead, absolutely incredibly far ahead, but then we had a couple of other reputable polls - tracking polls like the L.A. Times poll and a couple others - actually showing Donald Trump being basically even with Hillary. If you split the different they would just be at the margins of the confidence interval for normal kinds of polling."