U.S. population, and how many people do you have to poll?

U.S. population, and how many people do you have to poll?

When a poll tells us a candidate for president of the United States is favored by ___% of the population, they tell us it has a "margin of error" of +-__% .

For example, August 6, 2008, CBS poll on the president of the United States put John McCain with 39% of the vote and Barrak Obama 45% of the vote, with a margin of error of plus or minus 3 percentage points.

The World Fact Book reports U.S. population at over 300 million, 301,139,947 (estimate as of 2007).

How many people do you think you'd have to poll to get within plus or minus 3% or 300,000 of the correct vote?

10 million? 1 million? This particular CBS pre-poll accurately extrapolates the minds of over 300 million people by polling just 906 people, or .00009 % of the population.

We're not so different after all!

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