Jeffery再来问个题。

jeffery2541

4. GWD21-Q4:
Which of the following most logically completes the passage?

Appendicitis (inflammation of the appendix) is potentially fatal; consequently, patients with symptoms strongly suggesting appendicitis almost always have their appendix removed. The appropriate surgery is low-risk but performed unnecessarily in about 20 percent of all cases. A newly developed internal scan for appendicitis is highly accurate, producing two misdiagnoses for every 98 correct diagnoses. Clearly, using this test, doctors can largely avoid unnecessary removals of the appendix without, however, performing any fewer necessary ones than before, since ______.

A.the patients who are correctly diagnosed with this test as not having appendicitis invariably have medical conditions that are much less serious than appendicitis
B.the misdiagnoses produced by this test are always instances of attributing appendicitis to someone who does not, in fact, have it
C.all of the patients who are diagnosed with this test as having appendicitis do, in fact, have appendicitis
D.every patient who is diagnosed with this test as having appendicitis has more than one of the symptoms generally associated with appendicitis
E.the only patients who are misdiagnosed using this test are patients who lack one or more of the symptoms that are generally associated with appendicitis

答案给的是B，可是我选的是C。

keithyang926

这个问题比较清楚。

重点就在‘two misdiagnoses for every 98 correct diagnoses’和‘without, however, performing any fewer necessary ones than before’。

因为100个diagnoses里有2个是mis的，要保证不会performing any FEWER NECESSARY ones than before, 就必须要求上面两个misdiagnoses不会漏掉necessary的情况，也就是B答案讲的，本没有炎症的人被misdiagnose有了。这样，perform了两个unnecessary但没遗漏任何一个necessary。

jeffery2541

这个问题比较清楚。

重点就在‘two misdiagnoses for every 98 correct diagnoses’和‘without, however, performing any fewer necessary ones than before’。

因为100个diagnoses里有2个是mis的，要保证不会performing any FEWER NECESSARY ones than before, 就必须要求上面两个misdiagnoses不会漏掉necessary的情况，也就是B答案讲的，本没有炎症的人被misdiagnose有了。这样，perform了两个unnecessary但没遗漏任何一个necessary。

-- by 会员 keithyang926 (2012/8/13 13:47:49)

嗯嗯。谢谢keith。我终于明白啦。

我发现一个问题，好多时候做不出来正确的选项的原因正是理解不了文段的逻辑，找不到文段的重点。