# Dividing percentage

A book I'm now reading, "Apache Mahout Cookbook" by Pierro Giacomelli, states that

To avoid [this], you need to divide the vector files into two sets called the 80-20 split <...> A good dividing percentage is shown to be 80% and 20%.

Is there a strict statistical proof of this being the best percentage, or is it a euristic result?

• What do you do with that split? Can you give us more context on that? Feb 11 '15 at 13:44

• As we know, 80/20 rule aka Pareto principle is based on on the Pareto distribution. Consequently, the 80/20 split is based on the specific value of the Pareto index ($\alpha \approx$ 1.161). What I'm curious about is whether the two-way and three-way data splits have an analytical solution, based on the parameters you've mentioned ("sample size, distributions and relationships between your variables") as well as Pareto distribution's parameters. Feb 11 '15 at 14:16