请教大全-2-19,大全-2-20

joywzy · 发表于 2003-4-10 17:59:00

Questions 19-20 are based on the following.
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.
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.
(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.

20. Which of the following inferences about the conse-quences of instituting the new tests is best supported by the passage above?
(A) The incidence of new cases of NANB hepatitis is likely to go up by 10 percent.
(B) Donations made by patients specifically for their own use are likely to become less frequent.
(C) The demand for blood from blood banks is likely to fluctuate more strongly.
(D) The blood supplies available from blood banks are likely to go down.
(E) The number of prospective first-time donors is likely to go up by 5 percent.

19, ans: A, 20, ans: D
19, I choose C, 20, I choose A

这两题题干和选项都很清楚,可是我做错了,而且也不明白这两题思路如何?请问这种数字类的逻辑题有什么好办法吗?

谢谢.

cranberry · 发表于 2003-4-10 19:50:00

the first 用取非的办法，可以导出A是结果
the second 我不清楚你选A的道理，D是显而易见的结果？虽说是数字，但数字只是以另一种方式提出事实，所以还是要根据题干和题支的情况决定使用的方法。

shany · 发表于 2003-4-10 23:23:00

1. The answer C undermines the conclusion, surely can not be an assumption.
2.A is flawed. Instead,we can expect that the incidence in patients who receive blood donation may drop, due to the new screening system.
Because 5 percent of all prospective blood donors will be cleared out for donation, the total available blood supplies have to be down.

siebel · 发表于 2003-4-11 07:12:00

数字题，我觉得，一定要想清楚是怎样推出结论的，即：先把数学推导部分搞定。另外：数字是不可以怀疑的。

19. 数学推导可得，about 10 percent of actual donors will still supply NANB-contaminated blood.

答案A表明：有病捐血者不会因为其他原因而被排除在外。即：没有其他可能使这个10%降低，当然就是原题的assumption了。

C underestimated 竟然怀疑数学推导，斯拉斯拉迪油。

joywzy · 发表于 2003-4-11 08:44:00

cranberry,shany, siebel, 非常感谢.终于明白了.

luoyao307 · 发表于 2005-8-22 09:09:00

我想问一下19题中B答案“at any point”是什么意思？

hotlinda · 发表于 2005-11-22 10:30:00

at any point-任何情况下

xjlv128 · 发表于 2006-5-30 07:57:00

终于明白料！

MaccMichAA · 发表于 2006-9-3 17:35:00

菜妹我还是不懂D怎么推出来的...

向上爬的猪 · 发表于 2006-11-29 14:16:00

献学的人少了5%,那学的来源不也就少了嘛

请教大全-2-19,大全-2-20

请教大全-2-19,大全-2-20

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