Statistical maps are really a staristical graphic overlayed on a mapped surface. They are efficiently used to display numerical data over a selected region.
Found - http://images.google.com/imgres?imgurl=http://www.deepinfo.com/WorldGrid_1.jpg&imgrefurl=http://www.deepinfo.com/WorldGrid.htm&usg=__lCzKOwRrWt5AqV3rb38pgbkJOhA=&h=506&w=660&sz=102&hl=en&start=6&tbnid=31pQ8tHk53W4OM:&tbnh=106&tbnw=138&prev=/images%3Fq%3Dnumbered%2Bworld%2Bmap%26hl%3Den
This blog is a map catalog in which I am displaying fifty different types of maps and a tid-bit of information that looks into the purpose of the map!