来自《耶鲁大学开放课程：金融理论 第13集 第13集》

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  to minimize your expected penalty,
  来使预期的惩罚最小化
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  if the penalty is the squared error.
  如果惩罚是误差的平方
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  So because of that--
  正因为如此
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  so that's connected to a mathematical thing
  所以与数学的东西
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  and orthogonal vectors and all that.
  还有垂直向量有关
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  Because of that, the error we talk about always is the squared error.
  因此 我们说的误差是指误差的平方
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  And so that's whenever we're measuring uncertainty,
  当我们测量不确定性时
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  we're going to talk about the squared error,
  要说到误差的平方
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  the average of the squared errors--
  误差平方的平均数
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  or the square root of that, which is called the standard deviation.
  或者标准差 就是误差的平方根
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  Okay, I've one more minute to just finish this.
  好 我再讲一分钟
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  I'm assuming you all know that or can learn that.
  我假设那些你们都懂了