- 學位論文
大聯盟投手外部物質作弊事件研究
A Study of Pitcher Cheating in Major League Baseball
摘要
大聯盟投手是否作弊在手上塗抹外部黏性物質如松焦油、防曬乳，是一個缺乏明確證據的議題。按照聯盟的規則，投手不得在手上使用任何違法的外部物質，但近幾年官方沒有正視，加上裁判也未主動檢查下，已有不少關於投手作弊的傳聞。而投手使用外部物質的一項特點──投球轉速上升，使本文章可以透過轉速數據探討這項議題。 首先可以發現，聯盟於2021 年中嚴格執行外部物質審查政策後，投手平均轉速便出現驟降。接著發現當投手有動機作弊以爭取更好的表現時，例如合約年的自由球員或是高強度的對戰賽事，皆可以發現投手轉速相對變高，而當聯盟政策實施後，這些上升的轉速便消失，代表這些情況下投手十分可能是藉外部物質作弊。 此外，透過MNL模型分析該季逐球資料，可以發現轉速的上升能增進投手表現，包含增加打者揮空、好球判決以及降低打者擊球進場的相對機會。最後實際估算投手作弊對其帳面數據的效果。本文利用近年才出現的轉速資料，也為職業運動賽事作弊增添一新研究。
並列摘要
Whether Major League Baseball pitchers cheat by using foreign substance such as pine tar, sunscreen on hands is an issue lack of evidence. According to league rules, pitchers are not allowed to use any illegal foreign substances on their hands. However, MLB officials have not paid attention to it over the past few years, and referees have not checked for foreign substance. Therefore, there have been many rumors about pitchers cheating. An increase in spin rate on a baseball is one of characteristic that pitchers using foreign substances, which allowed us to do research on this topic. First of all, we found that after strict implementation of the foreign substance rules policy in mid-2021, the average spin rate of pitchers has decreased. Then, we found that when pitchers are motivated to cheat, such as free agent in contract-year or matchup between good record teams. Under these circumstances, spin rate of pitchers are increased, but after the league policy is implemented, these increment are disappeared, which means the pitchers are likely to cheat in these cases. In addition, by analyzing the pitch-by-pitch data for 2021 season using MNL model, we found that the increase in spin rate can improve the pitcher performance, including increasing the chance batter swinging strike, called strike and decreasing the chance batter hit into play. In the end, we estimate the effect of pitcher cheating. Our research apply the spin rate data appeared in recent years, and adds a new study of the field of cheating in professional sports.
參考文獻
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