WASHINGTON -- Here’s a survey: Is campaign polling 1) an art, 2) a science or 3) an act of statistical sleight of hand? The answer can be all of the above. As election season nears, polls are ramping up. It can be hard to interpret their terminology, let alone know which numbers to trust.

“All polls are not created equal,” said Lee Miringoff, the director of the Marist Institute for Public Opinion, which conducts the McClatchy-Marist poll. “And that’s unfortunate, because it all looks very scientific.”

So what should you look for? Are registered voters the same as likely voters? Can you define “margin of error”? How about “house effect”?

If it’s a good poll, the polling firm will disclose how the survey was conducted. These are guides to determine whether the poll is any good.

“It’s the responsibility of the reader to be smart, to be educated, to make the effort,” said Paul Freedman, a political science associate professor at the University of Virginia.

With the help of top pollsters and analysts, here’s an easy guide for wading through the coming deluge of polls about this year’s elections.

How was the sample picked?

In a reliable poll, all possible respondents have a known chance of being chosen. Polls such as Gallup and Marist have a dialing service that selects randomly from a list of every phone exchange in the country and combines random digits to generate phone numbers. When someone answers, a person who’s working for the poll asks the questions.

One benefit of the human touch: It would be easier for callers to skip the people who say they’re busy or answer the phone angrily, Miringoff said. But if callers don’t persevere, “you end up with a sample of friendly respondents with a lot of time on their hands,” he said.

What about cellphones?

It’s illegal to let a computer automatically dial a cellphone, and human dialers are more expensive. So automated polls, which don’t use human questioners, miss cellphones. But 30 percent of Americans now use cellphones instead of land lines, so it’s important to include them, said Frank Newport, the editor in chief of the Gallup Poll.

Who’s a likely voter?

Campaign polls usually sample either registered or likely voters. It’s more accurate to poll likely voters, because many registered voters – as many as 50 percent – won’t cast ballots.

Different firms have different ways of determining how to screen the sample for likely voters and they rarely disclose their methods, Freedman said. Common methods include asking whether the respondent plans to vote and whether he or she voted in the past, Miringoff said.

How were the questions asked?

A few words can make a huge difference. “Do you usually vote Democratic?” is more likely to generate “yes” responses than “Do you usually vote Democratic, or not?” When reporting results, Gallup includes question wording “down to the comma,” Newport said.

The order of questions is equally important, Miringoff said. Respondents will give the president lower approval ratings if they’ve just answered a string of questions about the tanking economy than they will if the approval rating comes first.