Classed Choropleth Maps

http://my.ilstu.edu/~jrcarter/Geo204/Choro/

Classed choropleth maps is a type of choropleth map that is combined into a smaller number of groups and portrayed in intervals.  Typically, four to seven classes are used to display the data.  In the classed choropleth map pictured, there are four classes to represent the amount of males per 100 females in each state in the United States.