MSNBC/National Journal: The Keith Olbermann number
Quantifying how voter indecision makes for highly volatile results
By Mark Blumenthal
Feb. 14, 2008
WASHINGTON - Viewers of MSNBC's "Countdown with Keith Olbermann" have become familiar with a new piece of polling nomenclature: The "Keith Number." What is that? "The margin of error plus the percentage reported as 'undecided,'" he explained when he first debuted it in early January, hoping to put a caveat on the poll numbers that had been so misleading in New Hampshire just a few days before.
But the Keith number was not a momentary whim. It now appears on the screen alongside poll results whenever they appear in Olbermann's broadcasts. You may think that a professional pollster would be horrified at this apparent departure from the "scientific" approach to survey research, but I am not horrified. In fact, aside from one small quibble, I like Olbermann's innovation....
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My only quibble is with Olbermann's emphasis on the undecided category for political horserace numbers. The problem is that polls show a lot of variation in "undecided" that has more to do with how the pollsters ask their questions than with the true level of certainty among the voters....
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Pushing hard for a choice near an election is a good thing, as some voters are reluctant to disclose their choice to a stranger, and the way voters lean at that stage is usually predictive of the way they will ultimately vote. When pollsters push hard many months before an election, however, the results can give a false impression that minds are made up, especially when one candidate has an early advantage in name recognition.
A far better measure of uncertainty is the follow-up question that Gallup and others have been asking this primary season immediately after asking about vote preference: "Would you say you will definitely vote for
, or is it possible you would change your mind between now and the election?" Before the South Carolina primary, four pollsters asked that question (or some variant) and found that between 18 and 26 of Democrats were either undecided or said they might still change their minds.
Add the "might change" number to the margin of error and we would have a version 2.0 of the Keith Number that accomplishes exactly what its namesake intended: A measure that indicates when poll numbers are more or less subject to change or volatility.
http://www.msnbc.msn.com/id/23166639/ 
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