阑尾炎ZHENTI求解

jackylin76

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 having 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

这题提供的答案是B，C错在哪里，实在想不明白，请NN指教。

arundhati

这道题的语言感觉怪怪的，感觉很不流畅～

题目说虽然判对精确率增加了，医生可以避免许多错判，但是判对的基本上没有变化。也就是说，事实上患病人群是被判为患病人群的子集。那么，多出来那部分就是将没病判有病了。这也是正如B所说的。

而C则将事实患病人群这个集合大于或等于被判为有病人群的集合，和文中相反，所以错误。

请指教！

sissi_woo

以下是引用jackylin76在2004-7-18 10:20:00的发言：

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 having 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

这题提供的答案是B，C错在哪里，实在想不明白，请NN指教。

我选择C。

题目的结论是：使用这个测试，医生们可以大量避免不必要的切除，并同时不减少必要的切除。

B：这个测试导致的误诊一直是将事实上患有阑尾炎的人诊断为未患有。

C：所有被诊断为患有阑尾炎的病人事实上都患有此病。

题干中的条件：以前的误诊率为20%，而这个测试的误诊率为2%，明显，新测试可以大量避免不必要的切除。C并且对这个测试的正确率作了界定：“所有被诊断为患有阑尾炎的病人事实上都患有此病”，所以C满足“大量避免不必要的切除，并同时不减少必要的切除”。

故此，我认为C对。

请NN们指正。

arundhati

sissi, 你对B的理解有点错误。

因为，B的实际意思和你理解的刚好相反，它实际是说把没有病的判为有病。而你刚好理解的相反，仔细看清哦～

同时C用了绝对话语言：所有被判的都有病。但其实题目已经说不是所有了，还有2％没有那。况且，正如我上面说的，C改变了集合范围。

请指教！

cranberry

b是说把没病的误诊为有病。

c的错误在于，即使它诊断有病的都是有病的，并不能避免其诊断没病的实际是有病的，结果和结论相矛盾。只说一面是不行的。

sissi_woo

以下是引用arundhati在2004-7-18 21:19:00的发言：

sissi, 你对B的理解有点错误。

因为，B的实际意思和你理解的刚好相反，它实际是说把没有病的判为有病。而你刚好理解的相反，仔细看清哦～

同时C用了绝对话语言：所有被判的都有病。但其实题目已经说不是所有了，还有2％没有那。况且，正如我上面说的，C改变了集合范围。

请指教！

啊，arundhat mm, cranberry dd, 谢谢你们的提醒!!

你的理解是对的。早上一爬起来就昏头啦  

[此贴子已经被作者于2004-7-18 23:06:12编辑过]

jackylin76

如果b是说把没病的误诊为有病,那unnecessary removals的可能性还是大呀.

不是和题干中的doctors can largely avoid unnecessary removals of the appendix相矛盾吗?

fair_sword

B对，可以把没有病得误诊，但是如果把有病得诊不出来，哪就有死人呢了

wanze

i agree with  jacklin76's point of view.

please explain it to us more sufficiently.   fair sword

sissi_woo

这个意思是说：新测试的误诊是将没有患阑尾炎的人也诊断为患有此病，所以，它最大限度地保证了必要的切除。套用一句话就是：“宁可错杀一千，不可放过一个”。呵呵~~