GWD-21-4

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 ______.

1. the patients who are correctly diagnosed with this test as not having appendicitis invariably have medical conditions that are much less serious than appendicitis
2. the misdiagnoses produced by this test are always instances of attributing appendicitis to someone who does not, in fact, have it

3. all of the patients who are diagnosed with this test as having appendicitis do, in fact, have appendicitis
4. every patient who is diagnosed with this test as having appendicitis has more than one of the symptoms generally associated with appendicitis
5. 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

why B? please explain the reason, thanks!

我说说我的理解

过去的有20%为unnecessarily surgery
                

现在新的只有二个为error diagnoses.而其它98为correct diagnoses.

结论Clearly, using this test, doctors can largely avoid unnecessary removals of the appendix without, however, performing any fewer necessary ones than before, since ______.

其实这类似找assumption……就是要有B这个前提你才能推出结论啊….

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
            ->IR

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
            ->这不就WEAKEN新技术好

D.         every patient who is diagnosed with this test as having appendicitis has more than one of the symptoms generally associated with appendicitis
            ->IR

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->IR

这样理解对不对？

准确率提高了，（原来需要做手术的人现在不用做了: 没必要），但是手术总次数并没改变

原因：原来不需要做手术的，现在要做了。have not, have it.

过去Unnecessarily->割了但是本可不用割

                                      Or 错误诊断为20%可能事实上有或没有的人

现在new technology->割了但是为必须

Or是现在的错误诊断为事实上没有的人

呼…差点被楼主搞晕..汗……

请楼主指正

我的理解，如果有不对的地方，请各位指正！

B和C的区别就在于最后一句话中的黄色字体“without, however, performing any fewer necessary ones than before”，这里应该注意“however”。我对选项C的理解和楼上一样，应该是support，不是weaken。从意思上看，B和C都对，但是如果加上however，我想B是最合适的答案。新的方法虽然被诊断出have it，则一定have it，但是有些被误诊为not have it, in fact, have it。这样也就有了“without, however, performing any fewer necessary ones than before”，因为有些necessary也被误诊为unnecessary。

虽然：过去Unnecessarily->割了但是本可不用割 ，但也存在，未被发现出来的病例。

呼…这道大家好像很晕吧...

我再说说我的看法

现在的new technology具备2种条件

1.减少不该割而割

2.该割都割了

ANS:B表示由这TEST产生的错误诊断总是将有A的归于没有A的人

第一大家要有doctor必有误诊的情况发生不论以前或现在的前题假设

因此B的意思简单的说就是:有病看做没病,

这意味着另一种误诊情况:将无病看做有病的机率会“低.”(就是不会有割错的情况产生,该割的都割了),因此ANS:B符合上述2个条件

C是个tricky的选项

C表示所有病人被诊断有A事实上就有A,也就是诊断有的确实都割了,意味诊断无误,但不保证诊断没有的确实没有,所以诊断没有的C选无法证明

若2%为没有而你诊断有->那不就白割了违反第二个条件

注意题目给2%是misdiagnoses

请指教