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十个馒头 · 2022年07月05日

如何判断考点？

  1. CFA I
  2. Quantitative

NO.PZ2015120604000076

问题如下：

According to the above table, and we are informed that the performance of next day is good, what is the probability of today's performance is good?

选项：

A.

0.74.

B.

0.28.

C.

0.67.

解释：

C is correct.

We can use Bayes' formula to solve this problem.

A: today's performance is good.

B: next day's performance is good.

P(A|B)=P(B|A)*P(A)/P(B)=0.7×0.4/(0.4×0.7+0.2×0.3+0.4×0.2)

P(B|A)*P(A)=0.7×0.4=0.28

P(B)=0.4×0.7+0.2×0.3+0.4×0.2=0.42

P(A|B)=0.67

如何判断这是一个需要bayes公式解决的问题？

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已采纳答案

星星_品职助教 · 2022年07月05日

同学你好，

题目要计算的是条件概率P（ today is good| next day is good），

题干给的条件之一是条件概率P（next day is good| today is good）=0.70.

类似这种相互颠倒的情况，优先考虑能否用贝叶斯公式来解题。

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