Building on a sketch by cwinske, [url]http://www.geogebratube.org/material/show/id/35118[/url] Which Craig posted at [url]http://approachinfinity.blogspot.com/2013/04/geogebra-help.html[/url] There's an optional guessing game for the mean.
More GeoGebra at [url]mathhombre.blogspot.com[/url]