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Optimal Pythagorean exponents in the Korean pro-basketball
Journal of the Korean Data & Information Science Society 2019;30:987-95
Published online September 30, 2019;  https://doi.org/10.7465/jkdi.2019.30.5.987
© 2019 Korean Data and Information Science Society.

Jangtaek Lee1

1Department of Applied Statistics, Dankook University
Correspondence to: Professor, Department of Applied Statistics, Dankook University, Gyeonggi-do 448-701, Korea. E-mail:
jtlee@dankook.ac.kr

The present research was conducted by the research fund of Dankook University in 2019.
Received July 30, 2019; Revised August 23, 2019; Accepted August 25, 2019.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
The Pythagorean expectation was first introduced by Bill James (1980) to estimate the winning percentage for baseball teams. The formula has been extended to other sports such as basketball, hockey, football, and soccer. There are many studies done on the Pythagorean formula for baseball in Korean professional baseball. But there are few results about other sports. This paper discusses the optimal exponent value of Pythagorean expectation for KBL (Korean Basketball League) using RMSE and MAD. The data used are the result of all Korean professional basketball teams from the 2010-2011 to 2018-2019 regular seasons. Although the optimal Pythagorean exponent of NBA by year is generally considered to be between 13 and 17, it was between 10 and 13 in the KBL. In conclusion, it was found that it is preferable to use the exponent values near 7 for the middle level teams and the exponent values near 12 for the other teams.
Keywords : Exponent, KBL, Pythagorean expectation, winning percentage.