来自《耶鲁大学开放课程：金融市场 第2集 第2集》

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  That says that if you have independent probabilities,
  意思是 几个相互独立的事件
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  then the probability of two events
  其中两个事件同时发生的概率
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  is equal to the product of their probabilities.
  等于他们分别发生的概率的乘积
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  So, the Prob(A and B)= Prob(A)*Prob(B).
  用 Prob(A and B)= Prob(A)*Prob(B)表示
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  That wouldn't hold if they're not independent.
  如果A和B不独立 这个式子就不成立
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  The theory of insurance is that ideally an insurance company
  保险理论就是在理想状态下
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  wants to insure independent events.
  保险公司为独立事件承保
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  Ideally, life insurance is insuring people--
  理想状态下 人寿保险
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  or fire insurance is insuring people--
  或者是火灾险
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  against independent events,
  承保的对象都是独立事件
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  so it's not the fire of London.
  伦敦大火的例子不在讨论范围
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  It's the problem that sometimes
  有时候会出现这种问题