「薪水小偷」一詞時常用來稱呼簽完新約後表現下降的球員，這樣的行為在學術上稱為怠惰，此外有些球員在合約年時表現會異常得好，這樣的行為則被稱為合約年現象，球員若存在怠惰或合約年現象會大大影響球隊的表現，甚至球團的經營。因此，本研究使用了WAR這項球員表現指標來驗證怠惰與合約年現象存在與否，並透過預測模型來預測球員是否會怠惰，最後提供實務上的貢獻。
WAR(Win Above Replacement)是棒球界用來衡量球員表現的新指標，它是指一位球員比起同樣位置的替補級球員，能多為球隊帶來幾場比賽勝利。本研究使用20年期間的MLB自由球員數據，利用統計檢定比較「正常賽季」、「合約賽季」和「合約後賽季」的WAR差異，並且除了對全體自由球員檢驗外，也將球員分成簽訂複數年合約或簽訂一年合約的球員來分別檢驗，結果發現只有簽訂複數年合約的球員會有合約年現象，但無論是全體自由球員、簽訂一年合約、簽訂複數年合約的球員都會怠惰。
最後，為了預測球員是否會怠惰和找出怠惰的球員具備之特徵，本研究建立三個機器學習模型，並創立新的目標變數來歸類球員怠惰與否，發現會怠惰的投手和打者分別有不同的特徵，而預測結果也能幫助球團對新簽約的球員是否會怠惰有更可靠的判斷。

The word “slacker” is referred to the players whose performances are decline after signing up the new contract, which is academically called shirking behavior. On the other hand, some players’ performances are unexpectedly well in their contract year, which is called contract year phenomenon. If players are shirking or in the contract year phenomenon will strongly influence the team’s performance, even the club’s management. Therefore, this research will use the WAR, the players’ performances index, to verify whether there exist shirking behavior and the contract year phenomenon among the players’ performances. Also, this research will develop the prediction model to predict whether the player is shirking and provides some practical contributions.
WAR (Win Above Replacement) is the new index to measure the players’ performances in the baseball league, which referred that how many games a player would win for the team compared to a position player. This research will use the data of MLB free agents in 20 years and use statistical test to compare the WAR differences of “normal season”, “contract season” and “post-contract season”. In addition, the research will categorize whole players from signing up multi-year contract to signing up one-year contract for the testing. It terms out that only the players who sign up multi-years contract are in the contract year phenomenon. However, the result show that whether the whole free agent, signing up one-year contract players, or signing up double-years contract players would be shirking.
Finally, to predict whether the players will be shirking and to find out the features of shirking players, this research will develop three machine learning models to develop new variables to categorize the players into shirking or not shirking and will also find out the different features of shirking pitchers and batters separately. And the prediction result can help clubs for reliable judgement of whether new signed-up players will be shirking.

論⽂審定書................................................................................................................................ i
致謝........................................................................................................................................... ii
摘要.......................................................................................................................................... iii
Abstract .................................................................................................................................... iv
第⼀章 緒論.............................................................................................................................. 1
第⼆章 ⽂獻探討...................................................................................................................... 5
第⼀節、 怠惰理論SHIRKING ........................................................................................... 5
第⼆節、 合約年現象CONTRACT YEAR PHENOMENON .................................................... 8
第三章 研究⽅法.................................................................................................................... 10
第⼀節、 資料來源概述.................................................................................................. 10
第⼆節、 資料欄位定義與介紹...................................................................................... 11
第三節、 研究流程.......................................................................................................... 15
第四節、 預測模型.......................................................................................................... 18
第四章 研究結果.................................................................................................................... 20
第⼀節、 第⼀階段結果.................................................................................................. 20
第⼆節、 第⼆階段結果.................................................................................................. 38
第五章 結論與建議................................................................................................................ 45
第⼀節、 研究結論.......................................................................................................... 45
第⼆節、 研究限制與建議.............................................................................................. 46
參考⽂獻.................................................................................................................................. 49

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三、網路資料
綜合報導(2021年4月30日)。球評驚陳偉殷成「軟投派」，日媒曝台灣英雄暖心舉動。聯合新聞網。檢自：https://udn.com/news/story/7001/5424325

綜合報導(2021年5月12日)。別再說薪水小偷！邦賈納連5場好投寫百年神數據。聯合新聞網。檢自：https://udn.com/news/story/6999/5452587

Baseball Reference. (n.d.). WAR Comparison Chart. Retrieved from https://www.baseball-reference.com/about/war_explained_comparison.shtml

Slowinski, P. (2010). What is WAR?. Retrieved from https://library.fangraphs.com/misc/war/

Slowinski, P. (2012). fWAR, rWAR, and WARP. Retrieved from https://library.fangraphs.com/war/differences-fwar-rwar/