安在 · 2022年09月10日
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.
需要解答 画图法
NO.PZ2015120604000076问题如下 Accorng to the above table, anwe are informeththe performanof next y is goo whis the probability of toy's performanis goo A.0.74.B.0.28.C.0.67. C is correct.We cuse Bayes' formula to solve this problem.toy's performanis goonext y's performanis gooP(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=0.28P(B)=0.4×0.7+0.2×0.3+0.4×0.2=0.42P(A|B)=0.67 我的理解贝叶斯公式是P（A｜B）=P（B｜A）*P（A）/P（B），P（B｜A）=0.4*0.7，P（B）=0.4*0.7+0.2*0.3+0.4*0.2=0.42，P（A）=0.4，但是这样算下来跟答案不一样，是不是P（A）错了？
NO.PZ2015120604000076 问题如下 Accorng to the above table, anwe are informeththe performanof next y is goo whis the probability of toy's performanis goo A.0.74. B.0.28. C.0.67. C is correct.We cuse Bayes' formula to solve this problem.toy's performanis goonext y's performanis gooP(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=0.28P(B)=0.4×0.7+0.2×0.3+0.4×0.2=0.42P(A|B)=0.67 这个题目有问题吧？题目的意图是想考察条件概率，但是问法并不是，问的就是一个独立事件的概率。
NO.PZ2015120604000076 问题如下 Accorng to the above table, anwe are informeththe performanof next y is goo whis the probability of toy's performanis goo A.0.74. B.0.28. C.0.67. C is correct.We cuse Bayes' formula to solve this problem.toy's performanis goonext y's performanis gooP(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=0.28P(B)=0.4×0.7+0.2×0.3+0.4×0.2=0.42P(A|B)=0.67 这个题用贝叶斯公式怎么画图啊
NO.PZ2015120604000076 问题如下 Accorng to the above table, anwe are informeththe performanof next y is goo whis the probability of toy's performanis goo A.0.74. B.0.28. C.0.67. C is correct.We cuse Bayes' formula to solve this problem.toy's performanis goonext y's performanis gooP(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=0.28P(B)=0.4×0.7+0.2×0.3+0.4×0.2=0.42P(A|B)=0.67 如题
NO.PZ2015120604000076 问题如下 Accorng to the above table, anwe are informeththe performanof next y is goo whis the probability of toy's performanis goo A.0.74. B.0.28. C.0.67. C is correct.We cuse Bayes' formula to solve this problem.toy's performanis goonext y's performanis gooP(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=0.28P(B)=0.4×0.7+0.2×0.3+0.4×0.2=0.42P(A|B)=0.67 老师，这个式子完全没看懂，麻烦一下每一步。谢谢
