[求助]急问GWD15－35！谢谢！

殇阳雪

Q35:

For what percent of those tested for a certain infection was the test accurate; that is, positive for those who had the infection and negative for those who did not have the infection?

(1)     Of those who tested positive for the infection,  did not have the infection.

(2)     Of those tested for the infection, 90 percent tested negative.

                  

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.

答案是E. 为什么不是C呢。10％×（7/8)不可以么?

谢谢各位大牛了.

Q13:

Of the books standing in a row on a shelf, an atlas is the 30th book from the left and the 33rd book from the right.  If 2 books to the left of the atlas and 4 books to the right of the atlas are removed from the shelf, how many books will be left on the shelf?

 

A.    56

B.     57

C.     58

D.    61

E.     63

还有这个题,没太明白什么意思.....

[此贴子已经被作者于2008-2-25 15:51:49编辑过]

heslaw

题目要求

Sensitivity (test +ve,actual +ve) and Specificity (test -ve, actual -ve)

(1)     Of those who tested positive for the infection, 1/8 did not have the infection.

(2)     Of those tested for the infection, 90 percent tested negative.

	Patients with disease	Patients without disease
Test is positive	a	b
Test is negative	c	d

sensitivity = a / (a+c)        specificity = d / (b+d)

1告诉了我们b的值

2告诉了我们c+d

应该很清楚了吧？不知道c,d的分别值

殇阳雪

嗯.感谢heslaw!!偶后天就考了,这种题终于明白了!!

能不能再帮我看看13题呢,没太明白题的意思...

heslaw

左起数30

右起数33

一共62本书么

拿掉6

还有56

heslaw

我明天考

希望能记得一些jj给大家

殇阳雪

呵呵,原来这个意思呀,咳,最忌讳就是看不明白题了.

你这么强肯定没问题拉,我后天2战,上次就是裸考,所以心态平稳了.

heslaw

以下是引用殇阳雪在2008-2-25 16:08:00的发言：

呵呵,原来这个意思呀,咳,最忌讳就是看不明白题了.

你这么强肯定没问题拉,我后天2战,上次就是裸考,所以心态平稳了.

人生在世，潇洒裸一回也是很有意义的

elevenjy1107

我太喜欢你的ps了~~~~
有梦的人，没时间绝望。

加油~~~！