Good Question: How Do Polls Work?
MINNEAPOLIS (WCCO) -- The first Republican debate for President is less than two weeks away and sixteen candidates will be vying for ten spots. The people who make it to the stage will be determined by the average of five national polls.
So, how do polls work? Good Question.
According to Rob Daves, a public opinion research consultant, polls start with an unbiased questionnaire, a representative sample and a correct analysis of the data.
"It works just like it does at the clinic when you get your cholesterol tested," Daves said. "They don't have to take all of your blood to get the cholesterol test."
National polls often question 500 to 1000 people to get the pulse of the entire nation. Daves says people are chosen for polls at random.
"As long as it's random," he said. "It starts to fall apart when the principles of randomness are violated."
People without Internet access are traditionally underrepresented in Internet polling while people who don't speak English are generally underrepresented in phone polling.
"We have to take care of that on the back end by weighting," he said. "Weighting is not a bad thing."
Both cell and landlines are now called. Though considered less accurate, internet polling is becoming more common too.
"The thing about cellphone is it's hideously expensive to do that kind of dialing," said Daves. "You have to do the dialing by hand, according to federal law."
Estimates are it could cost between two to five more to poll this presidential election compared to last because there are more cellphones and a more diverse population.
When it comes to accuracy, Daves said the better, national polls are generally accurate. Polls are the most accurate the closer they are taken to election day. When Daves ran polling at the Star Tribune years ago, they polled up to the night before the election.
In 2014, the polls for Minnesota governor and U.S. Senate were very close, but the 2015 race for British Prime Minister underestimated the conservative vote.
Daves says when analyzing polls, it's important to look at what's being asked.
"Some measure favorability, some of them actually intent to vote and some measure who are you likely to support, which is not the same thing as voting," he said.
He recommends looking at polls in the aggregate on polling aggregator sites like Real Clear Politics or Huffington Post to get sense of who's ahead and offer balance to any polls that might lean a certain way.