Polling: The Math Behind The Madness

Correction Nov. 3, 2008

In this interview, we attributed the prediction that Dewey would defeat Truman in 1948 to the poll's reliance on the telephone, which slanted the sample toward wealthier people who owned phones. In fact, that problem occurred in 1936, when the "Literary Digest" surveyed people whose addresses were taken from phone books.

Who's up? Who's down? Who cares? Just how did this ubiquitous staple of political coverage come to be? And just what is that margin of error thing? Weekend Edition "math guy" Keith Devlin explains the origins of the mathematical formulas used in polling.

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