In country X, the probability that a letter sent through the postal system reaches its destination is 2/3. Assume that each postal delivery is independent of every other postal delivery, and assume that if a wife receives a letter from her husband, she will certainly mail a response to her husband. Suppose a man in country X mails a letter to his wife (also in country X) through the postal system. If the man does not receive a response letter from his wife, what is the probability that his wife received his letter?
解析
D is correct.
考点 Bayes' formula
解析
(Notices: if the wife did not receive the letter, she would not send response to the man.)
Note:
A: the wife received the letter; : the wife did not receive the letter;
B: the man received a response letter from his wife; : the man did not receive a response letter from his wife
The question "If the man does not receive a response letter from his wife, what is the probability that his wife received his letter?" is equal to figure out
不理解，为什么是2/5
