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🌊Yuri🌊 · 2022年11月29日

问

  1. CFA I
  2. Quantitative

NO.PZ2015120604000067

问题如下：

Which of the following statements is the most correct?

选项：

A.

If events A and B are mutually exclusive, then P(A or B)=P(A)-P(B)

B.

If events A and B are mutually exclusive, then P(AB)=P(A)×P(B).

C.

If events A and B are mutually exclusive, then P(A or B)=P(A)+P(B)

解释：

C is correct.

P(AB)=P(A)×P(B) is only correct when A and B are independent events. In this case, P(A/B)=0,P(AB)=0，because event A and B are mutually exclusive

老师我知道互斥的情况下ab等于0，但是c选项是怎么得来的呢

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1 个答案

星星_品职助教 · 2022年11月30日

同学你好，

1）根据加法法则，P(A or B)=P(A)+P(B)-P(AB)；

2）由于“events A and B are mutually exclusive”，所以P(AB)=0；

综上，当两个事件为互斥的时候，P(A or B)就等于P(A)+P(B)。具体公式见下图讲义截图。

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NO.PZ2015120604000067 问题如下 Whiof the following statements is the most correct? A.If events A anB are mutually exclusive, then P(A or B)=P(A)-P( B.If events A anB are mutually exclusive, then P(AB)=P(A)×P(B). C.If events A anB are mutually exclusive, then P(A or B)=P(A)+P( C is correct.P(AB)=P(A)×P(is only correwhen A anB are inpennt events. In this case, P(A/B)=0,P(AB)=0，because event A anB are mutually exclusive 为啥等于0 就等于PA+PB?

2022-11-30 05:54 1 · 回答

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2022-10-01 11:21 1 · 回答

NO.PZ2015120604000067 解析中说到In this case, P(A/B)=0, because event A anB are mutually exclusive. P(A/B)为什么不是等于P(A)+P(B)?

2021-07-20 18:30 2 · 回答

老师，我知道P（a|b）和P（ab）都得零，但是C咱们随便假设一下，如果说P（a）=0.3 P（b）=0.2 两个数一算最后也不得零啊 为什么选C呢？

2019-08-21 01:40 1 · 回答