Reporting on the 2006 Minnesota Senate campaign between Republican Rep. Mark Kennedy and Democrat Amy Klobuchar, Fox News' Carl Cameron falsely compared the results of "recent polls" that "gave Klobuchar a double-digit lead" with "the latest Zogby Internet poll [which] shows Kennedy within seven points." But the "Zogby Internet poll" Cameron cited is not a "scientific" poll of randomly selected participants.
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During a report on the 2006 Minnesota Senate campaign between Republican Rep. Mark Kennedy and Democrat Amy Klobuchar, Fox News chief political correspondent Carl Cameron falsely compared the results of "recent polls" that "gave Klobuchar a double-digit lead" with "the latest Zogby Internet poll [which] shows Kennedy within seven points." But the "Zogby Internet poll" Cameron cited is not "scientific": Rather than being randomly selected by the pollster from the general population, poll participants were randomly selected from a group of people who had access to the Internet, knowledge of the opportunity to participate in Zogby polls, and an interest in participating.
The other "recent polls" Cameron noted that show a "double-digit lead" for Klobuchar are "scientific polls" of registered Minnesota voters. A "scientific poll," according to the National Council on Public Polls (NCPP), is one in which "the pollster uses a specific statistical method for picking respondents." For example, the Minneapolis Star-Tribune's July 6-11 poll, which found Klobuchar leading Kennedy 59-42 among likely voters, used "Random Digit Dialing" to reach a sample of "all adults in the state who live in households with landline telephones ...; the sample was not limited to those with listed phone numbers, or newspaper subscribers, or other inappropriate populations."
By contrast, the "Zogby Internet" poll Cameron referred to appears to be a July 24 Zogby Interactive poll conducted for the Wall Street Journal Online. It found Klobuchar leading Kennedy, 49.4 percent to 42.9 percent. According to an explanation of the poll's methodology, rather than drawing from a random sample of likely voters in Minnesota, those selected to receive the survey were drawn from Zogby's list of people who wanted to participate in Zogby Interactive polls:
Online polls were conducted by Zogby Interactive, a unit of Zogby International of Utica, N.Y. Zogby has assembled a database of individuals who have registered to take part in online polls through solicitations on the company's Web site as well as other Web sites that span the political spectrum. Individuals who registered were asked to provide personal information such as home state, age and political party to Zogby, which in turn examined that data and contacted individuals by telephone to confirm that it was valid.
Zogby International telephoned about 2% of respondents who completed the interactive survey to validate their personal data. To solicit participation, Zogby sent emails to individuals who had asked to join its online-polling database, inviting them to complete an interactive poll. Many individuals who have participated in Zogby's telephone surveys also have submitted e-mail addresses so they may take part in online polls.
According to NCPP, in "unscientific polls, the person picks himself to participate."
In an April 26 post on his weblog Mystery Pollster discussing a Zogby survey conducted for the online gambling industry, Democratic pollster Mark Blumenthal highlighted the way in which the methodology for Zogby's Internet-based surveys diverges from that in polls based on a "'scientific' random sample":
Why is it important that the survey was conducted online?
1) This survey is not based on a "scientific" random sample -- The press release posted on the web site of the trade group that paid for the poll makes the claim that it is a "scientific poll" of "likely voters." As we have discussed here previously, we use the term scientific to describe a poll based on a random probability sample, one in which all members of a population (in this case, all likely voters) have an equal or known chance of being selected at random.
In this case only individuals that had previously joined the Zogby panel of potential respondents had that opportunity. As this article [link no longer operative; Google cache link is here] on the Zogby's web site explains, their online samples are selected from "a database of individuals who have registered to take part in online polls through solicitations on the company's Web site, as well as other Web sites that span the political spectrum." In other words, most of the members of the panel saw a banner ad on a web site and volunteered to participate. You can volunteer too -- just use this link.
Zogby claims that "many individuals who have participated in Zogby's telephone surveys also have submitted e-mail addresses so they may take part in online polls." Such recruitment might help make Zogby's panel a bit more representative, but it certainly does not trans[f]orm it into a random sample. Moreover, he tells us nothing about the percentage of such recruits in his panel or the percentage of telephone respondents that typically submit email addresses. Despite Zogby's bluster, this claim does not come close to making his "database" a projective random sample of the U.S. population.
Blumenthal's polling firm, Bennett, Petts and Blumenthal, has conducted polling (subscription required) on the Minnesota Senate race for the Democratic Senatorial Campaign Committee (DSCC). The latest DSCC poll, conducted by Blumenthal's firm from July 16-20, has Klobuchar leading Kennedy 50-34 among likely voters.
From the July 24 edition of Fox News' Special Report with Brit Hume:
CAMERON: While some recent polls gave Klobuchar a double-digit lead in this historically Democratic-leaning state, the latest Zogby Internet poll shows Kennedy within seven points. He's better funded, better known, and is the aggressor, trying to put Klobuchar on defense on security matters, particularly the war in Iraq.