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Sissiwonglx · 2022年06月01日

这道题其实没看懂

NO.PZ2015120604000074

问题如下:

According to the above table, which of the following statements is the most correct?


 

选项:

A.

The joint probability of  having a good today' performance and a netural next day's performance is 0.08

B.

The joint probability of  having a good today' performance and a netural next day's performance is 0.70.

C.

The joint probability of  having a good today' performance and a netural next day's performance is 0.20.

解释:

A is correct

PAB=PA/B×PB 

A means neutral performance

B means good economy

Therefore, The joint probability of  having a good today' performance and a netural next day's performance is 0.4×0.2=0.08

B

烦请老师仔细讲一下具体是怎么计算的,这个运算规则我没搞明白是怎么用在实际题目里的

1 个答案

星星_品职助教 · 2022年06月01日

同学你好,

本题要计算的是joint probability也就是P(AB),根据乘法法则,P(AB)= P(A)×P(B|A)

表格前两列代表今天发生的事件和对应概率。以下图为例,今天是“Good”的概率就是0.4,即P(A);

后两列代表在第一列事件发生的条件下,再发生第三列的事件的概率。下图中的0.2即表示在今天是good的条件下,第二天是neutral的概率,即P(B|A)。


所以,The joint probability of having a good today' performance and a netural next day's performance=0.40×0.20=0.08