请教（关于检验NANB）那道

redli

8. 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.
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.
(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.
(E) The donors who will still supply NANB-contaminated blood will donate blood at the average frequency for all donors.


选A，但我觉的C没错呀，解释里说它是削弱，我不理解，“估计5%，漏了10%，不是低估吗？”

Kilroy

题目中说筛选方法估计可以去掉的不合格血样占总人数的5%，但他们还是遗漏另外2/3的不合格血样，算出来占总人数的10%。换句话说，就是一共有15%的不合格血样，检测出5%，漏掉10%。它的结论是还有10%的人的血样有问题，与前面的数字一致。那中间肯定没有别的传染引起的不合格血样增加，不然它的数字肯定要超过10%。也就是A

redli

我再看题时发现了我的错误
C：我当时错误的将“estimated to disqualify up to 5 percent of all prospective blood donors”与 “they will still miss two-thirds of donors carrying NANB hepatitis”分开来理解，其实这句话都是ESTIMATED的内容，所C选项其实是削弱。
我同意选A，但理解与你不同，它的意思是“这些Donors carrying NANB hepatitis 不会携带其他传染病而被其它常规检查检测出不合格。因为如过是，被遗漏的Donors carrying NANB hepatitis 就不到10%”

z_weining

我们换个思路：把选项的大概意思拿出来，然后看看是不是和原文有关（至少要有两块有关）
a）献血者不会携带其他病毒。（和原文有两块一致，“献血者”，“携带”）
b）献血者不犯病。(只有“献血者”有关)
c）人数估计被低估了。（只有“人数估计”有关）
d）a,和b在c上比时，原文必须出现a,b,c。但是原文没出现过potential blood donors

Kilroy

我对楼上的这种方法的应用范围感到怀疑
有些题型，特别是解释现象题可能不符合这个规律