Regression toward the mean
In statistics, regression toward the mean is the phenomenon where if one sample of a random variable is extreme, the next sampling of the same random variable is likely to be closer to its mean. Furthermore, when many random variables are sampled and the most extreme results are intentionally picked out, it refers to the fact that a second sampling of these picked-out variables will result in "less extreme" results, closer to the initial mean of all of the variables.
Francis Galton's 1886 illustration of the correlation between the heights of adults and their parents. The observation that adult children's heights tended to deviate less from the mean height than their parents suggested the concept of "regression toward the mean", giving regression analysis its name.
Sir Francis Galton was a British polymath and the originator of the behavioral genetics movement during the Victorian era.
An 1882 portrait of Galton by Gustav Graef
Portrait of Galton by Octavius Oakley, 1840
Galton in the 1850s
Portrait by Charles Wellington Furse, 1903