http://commons.apache.org/math/
http://en.wikipedia.org/wiki/Percentile
http://en.wikipedia.org/wiki/Regression_analysis
http://www.mat.ufmg.br/~regi/gaalt/markov.pdf
http://wwwhome.math.utwente.nl/~litvakn/ISP/sheets_class5-6.pdf
http://www.math.wustl.edu/~feres/Math450Lect05.pdf