"Galton termed this phenomenon a regression towards mediocrity, which in modern terms is a regression to the mean. To a naïve observer, this might suggest that later generations are going to exhibit less variability--literally more mediocrity--than earlier ones, but that is not the case. It is a purely statistical phenomenon. Unless every child is exactly as the same size as the parent in relative terms (i.e., unless the correlation is exactly equal to 1), the predictions must regress to the mean regardless of biology if the mean squared error is to be minimized". people.duke.edu/~rnau/regintro.htm

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