大全-2-19

Blood banks will shortly start to screen all donors for NANB hepatitis. Although the new screening tests are estimated to disqualify up to 5 percent of all prospective blood donors, they will still miss two-thirds of donors carrying NANB hepatitis. Therefore, about 10 percent of actual donors will still supply NANB-contaminated blood.

大全-2-19.          The argument above depends on which of the following assumptions? E/A

(A) Donors carrying NANB hepatitis do not, in a large percentage of cases, carry other infections for which reliable screening tests are routinely performed.

(B) Donors carrying NANB hepatitis do not, in a large percentage of cases, develop the disease themselves at any point.

(C) The estimate of the number of donors who would be disqualified by tests for NANB hepatitis is an underestimate.

(D) The incidence of NANB hepatitis is lower among the potential blood donors than it is in the population at large.（A）

(E) The donors who will still supply NANB-contaminated blood will donate blood at the average frequency for all donors.

答案是A, 我选了E.  不是很明白, 请教. 谢谢.

原文说的5%对应1/3的donors carrying NANB hepatitis,所以文章说10%对应2/3的donors carrying NANB hepatitis.

可是要是A不成立的话,那文章说的10%是不一定对应2/3的donors carrying NANB hepatitis.也就是它的推论不成立.

麻烦竹子翻译一下原文吧，没看明白

从哪里看出：原文说的5%对应1/3的donors carrying NANB hepatitis,所以文章说10%对应2/3的donors carrying NANB hepatitis.

Although the new screening tests are estimated to disqualify up to 5 percent of all prospective blood donors, they will still miss two-thirds of donors carrying NANB hepatitis.

Blood banks will shortly start to screen all donors for NANB hepatitis. Although the new screening tests are estimated to disqualify up to 5 percent of all prospective blood donors, they will still miss two-thirds of donors carrying NANB hepatitis. Therefore, about 10 percent of actual donors will still supply NANB-contaminated blood.

大全-2-19.      The argument above depends on which of the following assumptions?

(A) Donors carrying NANB hepatitis do not, in a large percentage of cases, carry other infections for which reliable screening tests are routinely performed.

谢谢先，但是还是不明白...

两个范围的问题是么?

5%的人会被过滤掉，这5%对应的是1/3的病人被过滤掉...

看来我得放弃了 实在是想不明白 看了40分钟了

先谢谢斑竹帮忙解答和晴天小狗参与讨论。一直保持沉默，因为想了好几次没有想通。今天好象突然有了思路，是不是这么理解：

题目给出的论点是说新的技术只能发现1/3有这种毛病的人，那么这个论点的依据应当是，剩下的人由于其病症的特征是没法通过这种新技术或者是已有的任何老的技术能发现的，所以结论是有2/3的这种毛病的人是不能被发现的。因而答案A是对的。

不知道这样的思路和理解对不对？谢谢。

Although the new screening tests are estimated to disqualify up to 5 percent of all prospective blood donors, they will still miss two-thirds of donors carrying NANB hepatitis

5%对应1/3的donors carrying NANB hepatitis

好晕

I think we can forget about the 5% or 1/3 in the first place.  My view is that the key point is that some of the NANB-contaminated blood cannot be identified during the testing.  Then what is the assumption that such NANB-contaminated blood cannot be identified? - the answer should be that current testing method or the existing methods cannot identify them.  Or we can think in this way, what if the current testing method or the existing methods can locate them by whatever characteristics? then no NANB-contaminated blood will be omitted in the testing.

I agree this is very much confusing and I hope I could express myself more clearly.  What do you say about this thinking process. 

再来一记，看看是不是少晕点：

我觉得先不去想1/3啊，5%的问题。我们这么来想：题目说有个新的方法能够找出部分的这种病症的献血者，然后说但是还是会漏掉另外剩下的那些病症者。最后问我们这样的推理过程的依据是啥。

A说，这些患者并在较大共性的层面上存在一个症状(or whatever)是现有的检测方法去测试的 -- 即，如果存在这么一种共性的症状并且是被测试的指标之一，那么这些病人就不会在测试中被漏掉了，那么上面的推理结果就不会出现了。所以题目中的表述成立的依据就是A成立。

你觉得呢？

我只能先谢谢您的解释，过两天再看吧

有时候就是这样 脑子突然就迷了，越看越迷...