A baseball game analysis by an extraction of characteristic play sequence

In baseball games, a term of momentum affecting the flow of the game is used as a mental concept. A team can feel positive momentum during a game when the first batter in an inning gets a base; the following batters get runs more easily. Regarding psychological momentum, many folk theories are widely believed among baseball people. A more quantitative approach to folk theories on baseball games is required because these are qualitatively explained without any clear basis. In this article, we statistically analyze the plays on 31 games by National Institute of Technology, Nara College (NIT-Nara) team in Japan high school baseball tournament. The verification of typical folk theories associated with some specific plays shows that these theories are not statistically significant. The playing-style is checked by means of bias on the play frequency. It is found that negative plays occurred more often than those by the opponent teams. The evaluation for the plays with n-gram frequency extracts some characteristic play sequences. These analyses revealed that NIT-Nara team is rather emotionally unstable to keep their positive momentum. Furthermore, a method for detailed investigation of the key plays driving momentum on the game is mentioned as the future problem.