Choropleth Map: Classed

http://my.ilstu.edu/~jrcarter/Geo204/Choro/Tom/
While choropleth refers to any map that portrays areal data, whether it is classed or not distinguishes between different choropleth maps. The data on the map of California above is classed, meaning that the data it is portraying is grouped together in intervals by some particular method. There are multiple methods of grouping, or classifying, this data together, and whichever method to use is up to the cartographer, a lot of it depending on how many intervals are desired. The percent of Black condo owners in California is here classed into equal steps of 5%. The gap between each corresponding interval is numerically equal, so it is clear that the cartographer used the "equal steps" method of classification here.