The margin of error is an expression of the extent to which a poll's reported percentages would vary if the same poll were taken multiple times. The larger the margin of error, the less confidence one has that the poll's reported percentages are close to the "true" percentages, i.e. the percentages in the whole population. The margin of error can be calculated directly from the sample size (the number of poll respondents) and may be reported at different levels of confidence - the 99 percent level is more conservative, while the 95 percent level is more common.

Read the rest of this article: http://en.wikipedia.org/wiki/Margin_of_error

Today's selected anniversaries:

202 BC At the Battle of Zama, Carthaginian general Hannibal was defeated by Roman proconsul Scipio Africanus, ending the Second Punic War. (http://en.wikipedia.org/wiki/Battle_of_Zama)

1781 After losing the Battle of Yorktown, British forces led by Lord Charles Cornwallis officially surrendered, ending the American Revolutionary War. (http://en.wikipedia.org/wiki/American_Revolutionary_War)

1943 Streptomycin, the first antibiotic remedy for tuberculosis, was first isolated by researchers at Rutgers University. (http://en.wikipedia.org/wiki/Streptomycin)

1985 The first Blockbuster Video store opened in Dallas, Texas. (http://en.wikipedia.org/wiki/Blockbuster_Video)

1987 Black Monday: The Dow Jones Industrial Average fell by 22%, the largest one-day decline in history. Stock markets around the world soon followed with similar collapses. (http://en.wikipedia.org/wiki/Black_Monday)

Wikiquote of the day:

"These children that you spit on as they try to change their worlds are immune to your consultations. They're quite aware of what they're going through..." ~ David Bowie (http://en.wikiquote.org/wiki/David_Bowie)