Anscombe's quartet comprises four datasets that have nearly identical simple descriptive statistics, yet have very different distributions and appear very different when graphed. Each dataset consists of eleven (x, y) points. 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".

Data

For all four datasets: The quartet is still often used to illustrate the importance of looking at a set of data graphically before starting to analyze according to a particular type of relationship, and the inadequacy of basic statistic properties for describing realistic datasets. The datasets are as follows. The x values are the same for the first three datasets. It is not known how Anscombe created his datasets. Since its publication, several methods to generate similar datasets with identical statistics and dissimilar graphics have been developed. 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.