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标题: gwd-18-15 一个NN解释了，貌似对了，但还是有问题的 [打印本页]

作者: spritejudy 时间: 2006-10-18 17:14
标题: gwd-18-15 一个NN解释了，貌似对了，但还是有问题的

Q15:

Fact: Asthma, a bronchial condition, is much less common ailment than hay fever, an allergic inflammation of the nasal passages.

Fact: Over 95 percent of people who have asthma also suffer from hay fever.

If the information given as facts above is true, which of the following must also be true?

A.
Hay fever is a prerequisite for the development of asthma.

B.
Asthma is a prerequisite for the development of hay fever.

C.
Those who have neither hay fever nor asthma comprise less than 5 percent of the total population.

D.
The number of people who have both of these ailments is greater than the number of people who have only one of them.

E.
The percentage of people suffering from hay fever who also have asthma is lower than 95 percent.

FACT1: P(A)<(F)

FACT2: P(F|A)=P(AF)/P(A) >95%

SO: P(A|F)=P(AF)/P(F)< P(AF)/P(A)<95%-->E

以上引用，但是，小于一个>95%的数就一定小于95%了吗？当然不一定咯

还是ETS没考虑这么多？

作者: spritejudy 时间: 2006-10-18 19:08
?

作者: spritejudy 时间: 2006-10-19 22:08
？

作者: rachelchen52 时间: 2008-12-3 07:59

FACT1: P(A)<(F)

FACT2: P(F|A)=P(AF)/P(A) >95%

SO: P(A|F)=P(AF)/P(F)< P(AF)/P(A)<95%-->E

我也觉得这样推导有问题。

1.P(F|A)=P(AF)/P(A) >95%没问题，

2.P(A|F)=P(AF)/P(F)，

因为P(A)<(F) ，

所以P(AF)/P(A) > P(AF)/P(F)没问题，

结合1.P(AF)/P(A) >95%

不必然推出 P(AF)/P(F) < 95%啊，因为P(AF)/P(F)有可能=95%啊。。。

另外：

Fact: Asthma, a bronchial condition, is much less common ailment than hay fever, an allergic inflammation of the nasal passages.

Fact: Over 95 percent of people who have asthma also suffer from hay fever.（这里的95%是说：在得A病的人里有95%的人也得F）

If the information given as facts above is true, which of the following must also be true?

A. Hay fever is a prerequisite for the development of asthma.

B. Asthma is a prerequisite for the development of hay fever.

C. Those who have neither hay fever nor asthma comprise less than 5 percent of the total population.

D. The number of people who have both of these ailments is greater than the number of people who have only one of them.

E.
The percentage of people suffering from hay fever who also have asthma is lower than 95 percent

（这里的percentage是不是说得H病的人里有A病的比例，我觉得画个图很清晰地可以看出：F集合里也得A的部分很少很少，因为根据第一句话：Asthma, a bronchial condition, is much less common ailment than hay fever）

画图时画一个小小圆（因为much less common）表示A病集合，再画一个大大圆表示F病集合，A图多于95%的部分画在F大圆里，可以清晰地看出F里面是A的部分很少很少，不可能等于或超出95%，否则“much less common”就不能成立。。。

以上是我的理解，不知道对否。。。

作者: won872 时间: 2008-12-9 06:30

Asthma , is much less common ailment than hay fever

Over 95 percent of people, who have asthma, also suffer from hay fever

Or to say 95% of asthma people have fever

Ask: how many % of Hey fever people has asthma?

Make a small circle for Asthma;

Make a big circle for Hay fever;

They have common intersection area, and mark it with gray color.

If the intersection area is 95% of Asthma, the small circle, it is for sure less than 95% of Hay fever, the big circle.

Conclusion, the percentage for people having both type of diseases constitute bigger percentage for the the uncommon disease as for the more common diseases.

作者: 双鱼游 时间: 2010-9-20 11:28
we know more people have hay fever than asthma

so let us take the worst case
A = 100 people
H = 101 people

we also know that out of 100 people with asthma 95 have hay fever so teh percentage in choice E is

95/101 which is qlways less than 95% for the worst case.

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