How far from reality the poll results can be expected to be is called the margin of error. The larger the sample polled, the smaller the margin. Statisticians calculate that the margin of error for a sample that size is 4 percentage points. That means that if every adult in the state were questioned, between 14 and 22 percent would say they are very concerned about job security. A smaller sample would have a larger margin of error.
Good pollsters strive for randomness.
Theoretically, every person in the target population should have an equal chance of being surveyed. That's where the Literary Digest poll fell short. So wealthier voters were over-represented in the sample, and the poll results were skewed. Today many pollsters dial phone numbers at random, so people with unlisted numbers will have as much chance of being sampled as people listed in phone books. Polls can be conducted in person, by telephone or by mail.