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Sep 25 / Jonathan

Polling: the cell phone effect

Sam Wang of the Princeton Election Consortium estimates the cell phone effect at about 1%. What’s the cell phone effect? The general idea is that a) pollsters mostly don’t call cell phones, b) more and more people have only cellphones and are thus not included in polls, and c) those people may have systematically different political views than the rest of the population (for example, they might be younger, and younger voters might tend to favor one candidate over another).

The cell phone effect: about 1 percent

How much has cell phone usage affected the reliability of polls? The answer may surprise you: Depending on what pollsters do about it, not much at all. Obama’s support may be understated by as little as 1%.

The question of whether polls have systematic errors is a continuing one. In the recent polling news is a Pew Center study that hits hard on the question of cell phone users. According to the survey, failing to survey people who have cell phones but no landline leads to a net underestimate of Obama’s support relative to McCain. According to a previous Pew/AP survey, cell-onlys comprised nearly 13% of households at the end of 2006. Cell-onlys prefer Obama over McCain by 18-19% (compared with an even split in the landline sample). Uncorrected, this leads to an error of about 0.13*0.185 = 2.4% in the Obama-McCain margin. Clearly this is significant, which is the Pew Center’s conclusion.

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