29.An insurance company has a paper record and an electronic record for every claim. For an inaccurate paper record, 60% chances that the electronic record is inaccurate. For an inaccurate electronic record, 75% chances that the paper record is inaccurate. 3% of all the claims are inaccurate both in paper record and in electronic record. Pick one claim randomly, what are the chances that it is both accurate in paper record and in electronic record?
A.97% B.94% C.68% D.65% E.35%
【确定】B 94%,
For an inaccurate paper record, 60% chances that the electronic record is inaccurate.
x * 60% = 3% x = 5% (inaccurate paper record)
For an inaccurate electronic record, 75% chances that the paper record is inaccurate.
y * 75% = 3% y = 4% (inaccurate electronic record)
（=> 2% inaccurate paper record, accurate electronic record
=> 1% inaccurate electronic record, accurate paper record）
inaccurate paper record + inaccurate electronic record = （5+4-3）=6%
ans:94%
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the explanation is from David thx to him ^^作者: 卧室春竹 时间: 2003-1-3 20:36
俺没明白....
请教斑竹 详细描述一下 呵呵
我可能太笨了....作者: lisaislisa 时间: 2003-1-3 20:41
yea , I've got the answer , but don't have any idea with such a problem ...it's always confusing me
can I think about it this way
set there are 100 incorrect paper record , then the incorrect ele record are 60
and there are 100 incorrect ele record , then the incorrect paper recods are 75
the total 200 records ,3 are both incorrect in ele and paper record ...
hmn ... my idea blocks here ...
would any one go on ? and is this the right way out ??
David emailed me attempting to send my detail explaination , but sth wrong with Yahoo ...
^^作者: tongxun 时间: 2003-1-3 21:15
简单地说，就是：
设X个inaccurate paper record，
设Y个inaccurate electronic record
总CLAIMS 是I，则
X*60% = 3%*I， x = 5% *I
y * 75% = 3%*I， y = 4% *I
由于两者的交集是3% *I，所以真正的不合格的为5+4-3=6% * I
任选一个是错误的，6%*I/I =6%
因此，选一个是没错误的，就是94%作者: 卧室春竹 时间: 2003-1-3 21:20
对
有道理
破题 让我想了很久....
谢谢斑竹.. (舞跳得不错）作者: lisaislisa 时间: 2003-1-3 21:31
that's exactly what i want
thx ^^
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