From the New York Times What’s the Matter With Polling?
…As Nate Silver of fivethirtyeight.com recently observed, “The problem is simple but daunting. The foundation of opinion research has historically been the ability to draw a random sample of the population. That’s become much harder to do.”
…Robert M. Groves, the provost of Georgetown and a former director of the Census Bureau, cautions, “The risk of failures of surveys to reflect the facts increases with falling response rates. The risk is not always realized, but with the very low response rates now common, we should expect more failed predictions based on surveys.”
The new economics have driven many election pollsters to the Internet, where expenses are a fraction of what it costs to do a good telephone sample. However, there are major problems with Internet polls. First is what pollsters call “coverage error.” Not everybody is reachable online; Pew estimates that 87 percent of American adults are Internet users.
A much bigger issue is that we simply have not yet figured out how to draw a representative sample of Internet users. Statisticians make a primary distinction between two types of samples. Probability samples are based on everyone’s having a known chance of being included in the sample.
THE best survey organizations, like the Pew Research Center, complete about two of the more expensive cellphone interviews for every one on a landline. For many organizations, this is a budget buster that leads to compromises in sampling and interviewing. The second unsettling trend is the rapidly declining response rate.
One of the most prominent applications of survey research is election polling. In election years, much of the polling by Pew Research Center focuses on people’s issue preferences, engagement in the election, opinions about the candidates, views of the campaign and voter preferences.
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