Classed Choropleth Map

http://www.agocg.ac.uk/reports/visual/casestud/dykes/issue3_1.htm

The main objective of a classed choropleth map is to provide visualization of a how a measurement varies across an area. Shading is used to show this proportion of statistical measurements. Too many classes can make it more difficult to read and the colors could possibly distort the actual information. Typically, 4 or 5 classes are usually enough. The classed choropleth map above shows data for children between 0 and 15 years old. It has a five class scheme and manages to get an equal number of cases into each class.