求助 GWD-18-Q15

lanshichao90

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

 为什么选E？？

Redshoe08

我也搞不懂，ABD一定错。我比较偏向于C。假设有100个人，如第2个fact说的，有超过95个人这2种病都有，那么还要设想有些是有其中一种的，那么不患病的自然就要少于5个人了。。。

不明。。。。

greedier

Asthma 比hay fever少见很多

超过95%的asthma 患者同时有hay fever,

E hay fever患者同时还有asthma的低于95%

yumeeiko

我觉得应该是应该得那个hay fever比Asthma common，所以得hay fever的人比较多。如果画一下那个那个圆的图，就知道那个hay fever的圆比较大，那相交的面积占asthma的比较大，那自然占fever的就比较小。其实就是分母越大，结果越小的道理！～我是这样理解的，不知道对不对。。。

davidsfo

设换A的有X,患有B的有Y，且Ｘ＜Ｙ
患有ＡＢ的有　９５％Ｘ< 95%Y

无及天下

E -- 同时患两种病的人少于95%

 

可以用条件概率不严格描述：

 

因为asthma远少于hay fever, 也就是P(asthma)远小于1，例如20%，P(hay fever | asthma) > 95%

 

P(hay fever and asthma) = P(asthma) * P(hay fever | asthma) = 20%*95%

 

香香奶

X->(Asthma)
Y->(Fever)

X*Y/X > 95%  ---> Y > 95%

Y*X/Y = X = P(Fever & Asthma)/ P(Fever)

cuz Y > 95% and Y > X  ---> X < 95%
hence  suffering from hay fever who also have asthma < 95%