Polling, or survey research, contains many facets. A thorough understanding survey research is described in "How Polls are Conducted", an excerpt from Where America Stands, a book published by John Wiley & Sons, Inc., in 1997. In this essay, Gallup Poll editors address sampling probability, sample selection, sample size, survey interviews, survey questions, and interpreting the results.
Excerpt from How are polls conducted?
Public opinion polls would have less value in a democracy if the public -- the very people whose views are represented by the polls -- didn't have confidence in the results. This confidence does not come easily. The process of polling is often mysterious, particularly to those who don't see how the views of 1,000 people can represent those of hundreds of millions. Many Americans contact The Gallup Organization each year
1. to ask how our results can differ so much from their own personal impressions of what people think,
2. to learn how we go about selecting people for inclusion in our polls, and 3. to find out why they have never been interviewed.
The public's questions indicate a healthy dose of skepticism about polling. Their questions, however, are usually accompanied by a strong and sincere desire to find out what's going on under Gallup's hood. It turns out that the callers who reach Gallup's switchboard may be just the tip of the iceberg. Survey researchers have actually conducted public opinion polls to find out how much confidence Americans have in polls -- and have discovered an interesting problem. People generally believe the results of polls, but they do not believe in the scientific principles on which polls are based. In a recent Gallup "poll on polls," respondents said that polls generally do a good job of forecasting elections and are accurate when measuring public opinion on other issues. Yet when asked about the scientific sampling foundation on which all polls are based, Americans were skeptical. Most said that a survey of 1,500-2,000 respondents - a larger than average sample size for national polls -- cannot represent the views of all Americans.
In addition to these questions about sampling validity, the public often asks questions about the questions themselves -- that is, who decides what questions to ask the public, and how those looking at poll results can be sure that the answers reflect the public's true opinion about the issues at hand.
