How are CNN polls taken?
By Brooks Jackson/CNN
February 18, 1999
WASHINGTON (February 18) -- How is polling at CNN carried out?
Designing a poll begins with the questions. Experts at CNN and its polling partner, the Gallup Organization, first formulate the questions. While writing them, the two groups wrestle with the wording. Is it biased? Will people understand what's being asked?
Once the questions are settled, Gallup orders up a list of who will answer them. On average, Gallup completes just over 1,000 interviews to represent a nation of more than 270 million. But if it's a truly random sample, it's like stirring soup -- so that one spoonful will tell you what the whole pot is like.
This sample will be a list of telephone numbers generated by computer -- random digits, so even unlisted phones will be included. The calls go out from eight Gallup centers around the country.
Here's the main thing -- the phone in your home is just as likely to ring as any other in the whole country. The only exceptions: Hawaii and Alaska, because of the expense.
A computer dials the random numbers and interviewers often reach business, fax machine or computer lines.
Not every answer is counted equally. People with two home phone lines, for example, are twice as likely to be called, so their answers are weighted less heavily so two-phone households won't be over-represented.
Any poll has a margin of error. Mathematically, a truly random sample of 1,022 should, in 19 polls out of every 20, produce results that are within three percentage points of what we would come up with if we interviewed everybody with a telephone.
And of course everyone who does not have a telephone is missed. That's about 6 percent of the population, more often poor, Southern and African-American than the population as a whole.
But going door-to-door would be many times more expensive. And it's been a long time polling flunked the election test.
In 1996 CNN's last poll before election day showed Bill Clinton 52 percent, Bob Dole 41 percent and Ross Perot 7 percent. The actual vote: Clinton just under 50, Dole 42, Perot 8. Not bad.
And, next time we call, it could be your phone.
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