Classed Choropleth Map

http://images.google.com/imgres?imgurl=http://www.ilstu.edu/~jrcarter/Geo204/Choro/map-AmFact-4eqint-orange-80pct.jpg&imgrefurl=http://www.ilstu.edu/~jrcarter/Geo204/Choro/&h=312&w=520&sz=57&hl=en&start=20&tbnid=24j8JVFARwIw7M:&tbnh=79&tbnw=131&prev=/images%3Fq%3Dclassed%2Bchoropleth%2Bmap%26gbv%3D2%26ndsp%3D20%26hl%3Den%26sa%3DN

The above map is a classed choropleth map that shows the number of males per 100 females from the Census in the year 2000. A classed map groups data into classification intervals and then each interval is then assigned a graphic value that usually uses the principle of maximum contrast.