Statistics

Percent and Probability - Learn what a percent is and how to figure probability.
http://www.mathleague.com/help/percent/percent.htm

The Birthday Problem: A Short Lesson in Probability - Find out how likely it is that two people in a class have the same birthday. With an explanation of the math behind this problem and a simulation.
http://www.mste.uiuc.edu/reese/birthday/

Fact Finder Kids' Corner - The U.S. Census Bureau provides this site as part of their American FactFinder effort. The site provides facts about all of the states, in an age-appropriate format. There is a quiz, and an explanation of the Census.
http://factfinder.census.gov/home/en/kids/kids.html

NASS Kids - The National Agricultural Statistics Service provides some basic explanations of statistical terms, as well as games and puzzles.
http://www.nass.usda.gov/Education_and_Outreach/Lesson_Plans/

Using Data and Statistics - Learn about charts and graphs created from everyday examples. Also, learn to how to compute different types of average values, such as the mean or median.
http://www.mathleague.com/help/data/data.htm

Statistics - Article from Encarta Encyclopedia defines this branch of mathematics, offers a short history, and provides an overview of the study today.
http://encarta.msn.com/encyclopedia_761562521/Statistics.html