The Anscombe quartet is comprised of four scatterplots that have nearly identical correlations, as well as means and standard deviations, but disparate shapes. These graphs show the crucial role that data visualization plays in developing a sensible statistical model. The negative option is included to produce the mirror image graph.
Contributed by: Ian McLeod (University of Western Ontario)
This Demonstration is intended for introductory statistics courses.
 F. J. Anscombe, "Graphs in Statistical Analysis," The American Statistician27(1), 1973 pp. 17–21.