為什麼不將train_test_split 的 test_size調整為更小? - Cupoy

2019/06/27 上午 08:17

機器學習共學討論版

黃稚翔

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ml100-2

ml100-2-d46

想請問老師們，範例中的test_size為0.25，也就是說train_size是0.75

但是不將test_size調整為更小的原因是要預防overfitting嗎?                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             

(我自己有測試，將test_size設為0.1，acc可達0.977...)

回答列表

• 2019/06/27 下午 00:21
  Jimmy
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  Hi 稚翔!

  
  

  test size 的大小會跟你 data 的總數有關，如果資料量非常大，那切個 10% 的資料做 testing 其實也非常多。但如果今天的資料量比較少，假設只有 50 筆，那在切 10 % 就只有五筆，這麼小的測試資料其實很難評估模型的穩定性。

  
  

      

• 2019/07/15 上午 10:22
  張維元 (WeiYuan)
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  關於評估有兩種手法：

  
  

  1. 拆成 testing 跟 training ，是避免只有一組資料做模型，testing 可以用來驗證 training 的模型

  2. 分成多回合訓練再取平均的  Cross-Validation ，避免模型太貼近某一組 training-testing 的結果

  
  

  我覺得 2. 比較像是處理 overfitting 主要的做法