[問題]FeiFei 第6部分 Q1

[evelyn_yeh]

In an insurance company,each policy has a paper record or an elecric record or both of them. 60 percent of the policies having incorrect paper record have incorrect electric record. 75 percent of the policies having incorrect electric record have incorrect paper record. 3 percent of all the policies have both incorrect electric record and incorrect paper record .If we randomly pick out a policy,what is the probability that it is one having both correct electric record and correct paper record .

Ans.94%
我不能認同這個答案,請高手解惑之

[scujean]

~P表示不是P
0.6*~P=~P且~E--（3）
0.75*~E=~P且~E--（2）
0.03*all=~P且~E--（1）
（1）帶入（2）（3）
得~p=0.03all/0.6
~E=0.03all/0.75
題目要求[all-（~p+~E-{~p且~E}）]/all

[evelyn_yeh]

題目要求的是 "both correct electric record and correct paper record ".
但是,那並不等於 [all-（~p+~E-{~p且~E}）]
因為題目說 each policy has a paper record or an elecric record or both of them,
那麼 [all-（~p+~E-{~p且~E}）] 等於 P+ E-(p且E)
而題目問的是 (p且E) ,所以我認為無解呀...

discuss....

[FrankChang]

94%應該是P與E的聯集,至於題目沒錯的話似乎是問交集..

[scujean]

[all-（~p+~E-{~p且~E}）]/all
我寫的算式只能求出[a+b+c]/全 不能求出題目要求的 b/全
此題目有點問題
CD's pic

[evelyn_yeh]

此題目有點問題 ,所給的條件不足