Anscombe's quartet

Anscombe's quartet comprises four datasets that have nearly identical simple descriptive statistics, yet have very different distributions and appear very different when graphed.

They were constructed in 1973 by the statistician Francis Anscombe to demonstrate both the importance of graphing data when analyzing it, and the effect of outliers and other influential observations on statistical properties.

He described the article as being intended to counter the impression among statisticians that "numerical calculations are exact, but graphs are rough".

[7] Since its publication, several methods to generate similar datasets with identical statistics and dissimilar graphics have been developed.

[7][8] One of these, the Datasaurus dozen, consists of points tracing out the outline of a dinosaur, plus twelve other datasets that have the same summary statistics.

The four datasets composing Anscombe's quartet. All four sets have identical statistical parameters, but the graphs show them to be considerably different