Political Polls Without “Cell-Phone Only”s

by Devanshu Mehta

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Mark Blumenthal of Pollster.com summarizes a recent Pew study:

Today they released a new must-read report summarizing findings from “three major election surveys [conducted] with both cell phone and landline samples since the conclusion of the primaries.” The verdict? “Pew’s surveys this year suggest at least the possibility of a small bias in landline surveys.”

Skeptics don’t think that missing “cell-phone only” voters is a big deal for a variety of reasons. Weighting a poll by age demographics should already account for any missed voters, but that assumes that those with landlines vote similarly to those without. The average “cell-phone only” user tends to be younger and hence- presumably- an Obama voter.

A few days ago Nate Silver at the awesome FiveThirtyEight.com compared results from pollsters that include cell phones with a control group that does not and observed an approximately 2% bias against Obama in polls that did not include cell phones. The Pew study finds a similar effect.

Many people had predicted a similar effect in the 2004 election, but Bush’s margins over Kerry in the polls proved to be correct. Of course, there are many more people sans landlines in 2008 than there were four years ago.

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