Dan Judy’s comments to CNN on oversampling and claims that polling is deliberately overstating the standing of Hillary Clinton:
“Pollsters just saw this and rolled our eyes,” said Dan Judy, a Republican pollster for North Star Opinion Research.
“This is the classic case of people using an intentional or unintentional misunderstanding of polling to pretend results they don’t like are invalid,” Judy said. “Most voters aren’t that sophisticated when it comes to ins and outs of sampling and statistics and polling. But there are a lot of people spreading this around who know better — or should know better.”
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Here’s the reality about “oversampling.” Pollsters often dive deeper into certain subgroups (such as Latinos or African-Americans) to reduce their margins of error for those groups. Then they weight those groups to their actual proportion of the population.
Judy laid out an example.If he were polling 600 likely voters in a state with a 13% Hispanic population, that would mean 78 of the voters surveyed were Hispanic. “The margin of error of that is extremely high — it’s over 10 points — and you can’t at all break that down. You can’t say, ‘What do Hispanic men or Hispanic women think?’ You couldn’t do that with any degree of mathematical certainty,” he said.
So, instead, Judy said he’d call 300 Hispanic voters — enough to look at “men and women, Republicans and Dems, age breakdowns, regional breakdowns, and in a state like Florida some ethnic breakdowns — Cubans, Puerto Ricans, South and Central Americans. And when you run your survey numbers, you weight that 300 back down to 78.”
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