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Polling FAQ


Who Conducts Polls?


How are polls conducted?

Typically, the customer contacts the polling organization and places an order for a poll, specifying what questions are to be asked, when the poll will be conducted, how many people will be interviewed, and how the results will be presented. The pollster then calls the agreed upon number of people, asks them the questions. Usually, the interview begins with easy questions to assure the respondent that he or she is not going to be embarrassed. For example: "I am going to read you the names of some well-known political figures. For each one, please tell me if you have a favorable, neutral, or unfavorable opinion of that person." Then the names of well-known figures such as George Bush, Hillary Clinton, John McCain, et. are read. The answers are typed into a computer as they are given. When each interviewer has the requisite number of valid interviews, he or she transmits the results to the organization. When the poll is completed, the data are normalized if need be (e.g., to make sure men and women are equally represented), and the pollster prepares a final report, often breaking down the results by age, gender, income, education, political party, and other ways. The more people called, the more accurate the poll, but the more expensive it is. For state polls, 500-1000 valid interviews are typical (but it may take many times these numbers to get 500-1000 valid interviews). A state poll can easily run into the $15,000 ballpark.

How does the pollster decide who to call?

All polls are based on the idea of a random sample. Two methods are used to get the sample. The first is called RDD (Random Digit Dialing) in which the pollster carefully chooses an area code and prefix (together. the first six digits of a telephone number) and then picks the next four digits at random. Because of how the telephone is organized, people with the same first six digits generally live close together, although this property is changing. This method generates a good random sample since it hits all in the selected area with equal probability, including unlisted numbers. Unfortunately, it also hits business phones, fax machines, and modems. The second method takes telephone numbers from a telephone book or list and uses them or sometimes randomizes final digit to hit unlisted numbers.

Do pollsters call cell phones?


Do pollsters call VoIP phones?

Increasingly many people have phone service over cable or on Skype. There is no law against pollsters calling these phones, but it is a bit tricky because customers can often choose any area code they want. Someone living in Seattle can choose a Florida area code so his mother can call him as a local call. When a pollster calls someone with a Florida area code and gets someone in Washington, the accuracy of the poll is not improved.

Do pollsters miss any other large groups besides cell users?


Can polls be automated?


So polls done by human beings are more reliable?


Can a poll be conducted over the Internet?

Some companies, especially Zogby, have begun pioneering with Internet polls, usually by asking people to sign up. Obviously the sample is anything but random. Also people can lie, but they can lie on telephone polls, too Careful normalization can remove the sampling bias. For example, if 80% of the respondents in an online poll are men and the customer wants an equal number of men and women, the pollster can simply treat each woman's opinion as if four women said the same thing. Also, the online pollsters often poll the same people over and over, which has its advantages. For example, if a person has expressed strong approval for, say, George Bush five months in a row and now expresses strong disapproval, that represents a genuine shift. And, similar, to the robopollsters, every person gets precisely the same questions presented in precisely the same form, without any possible bias introduced by the interviewer.

Does it matter when the poll is conducted?


Can they tell who will actually vote?

  • Are you currently registered to vote?
  • Did you vote in 2004?
  • Did you vote in 2002?
  • Do you think your vote matters?
Some polling companies give the results based on all adults they survey. Others include only registered voters. Yet others include only likely voters, using their proprietary formula for determining who is likely to vote based on questions like those above. Depending on exactly how the voting questions are phrased and which category of respondents is included in the poll, some systematic bias may be introduced. Some pollsters publish the results for both likely voters and all registered voters. This site uses likely voters if there is a choice (not often).

What Does Margin of Error Mean?

There is no concept as confusing as 'Margin of Error.' It is used a lot but few people understand it. Suppose a polling company calls 1000 randomly selected people in a state that is truly divided 50-50 (say Missouri), they may, simply by accident, happen to call 520 Democrats and 480 Republicans and announce that Claire McCaskill is ahead 52% to 48%. But another company on the same day may happen to get 510 Republicans and 490 Democrats and announce that Jim Talent is ahead 51% to 49%. The variation caused by having such a small sample is called the margin of error and is usually between 2% and 4% for the sample sizes used in state polling. With a margin of error of, say, 3%, a reported 51% really means that there is a 95% chance that the true (unknown) percentage of voters favoring McCaskill falls between 48% and 54% [and a 5% chance that it is outside this (two sigma) range].

In the first above example, with a 3% MoE, the 95% confidence interval for McCaskill is 49% to 55% and for Talent 45% to 51%. Since these overlap, we cannot be 95% certain that McCaskill is really ahead, so this is called a statistical tie. When the ranges of the candidates do not overlap (i.e., the difference between them is at least twice the margin of error), then we can be 95% certain the leader is really ahead. The margin of error deals ONLY with sampling error--the fact that when you ask 1000 people in an evenly divided state, you are probably not going to get exactly 500 Democrats and 500 Republicans. However, a far greater source of error in all polls is methodological error.

What are methodological errors?

  • If the Senate election were held today, would you vote for the Democrat or the Republican?
  • If the Senate election were held today, would you vote for Sherrod Brown or Mike DeWine?
  • If the Senate election were held today, would you vote for Mike DeWine or Sherrod Brown?
  • If the Senate election were held today, would you vote for Democrat Sherrod Brown or Republican Mike DeWine?
  • If the Senate election were held today, would you vote for Republican Mike DeWine or Democrat Sherrod Brown?
  • If the Senate election were held today, for whom would you vote?
These questions will all get different responses.


Do pollsters present the actual numbers observed?


Which polls do you use?

First of all, only neutral pollsters are used. Pollsters whose primary business is helping Democrats or Republicans get elected are not used. They tend to make their horse look better. When there are multiple polls for a race, the most recent poll is always used. The middle date of the polling period is what counts (not the release date). If other polls have middle polling dates within a week of the most recent one, they are all averaged together. This tends to smooth out variations. In 2004, this algorithm did the best. Click on Polling data in Excel to the right of the map for all the raw polling data. It is sorted in descending order by polling date (Jan. 1 is 1.0). The fields are separated by commas so you can read the file into Excel.

What algorithm (formula) is used to compute the map?

In 2004, we ran three different algorithms. The main page just used the most recent poll. The second algorithm averaged three days' worth of polls using only the nonpartisan pollsters. The third one included a mathematical formula for predicting how undecided voters would break based on historical data. The second one was most stable and gave the best final result, so this time a slightly variation of it is used: The most recent poll is always used, and if any other polls were taken within a week of it, they are all averaged together. This method tends to give a more stable result, so the colors don't jump all over the place due to one unusual poll.

Should I believe poll results?

Sometimes. But you should try to get answers to these questions about any polls you see. Unfortunately, some pollsters are completely unethical, as described in this article.
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