Logically completes the passage

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Logically completes the passage

by punitkaur » Tue Dec 15, 2009 7:31 am
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 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

Can we use negation technique to verify our answers for such questions?

What category does this fall in? Most of the time I get my answers wrong to these questions because I dont know of a definite way to approach or look for. things like, should the answer be a paraphrase or can it contain new info?

Can someone suggest how to approach and what to look for in answers?

BTW OA is B
Source: — Critical Reasoning |

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by getso » Tue Dec 15, 2009 8:05 am
Nice Question.

I'm not sure of the approach.

OA is B

Even though test misdiagnoses 2 out of every 100, this is still fine as B says it attributes to someone who is not having appendicitis. Hence its not risker. however, if the results were other way round i.e if test missed 2 patients who are actually suffering then it was definitely risker to use this test.

@Testluv:Could you please help us in tackling such questions[/spoiler]

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by Testluv » Tue Dec 15, 2009 4:24 pm
getso wrote:Nice Question.

I'm not sure of the approach.

OA is B

Even though test misdiagnoses 2 out of every 100, this is still fine as B says it attributes to someone who is not having appendicitis. Hence its not risker. however, if the results were other way round i.e if test missed 2 patients who are actually suffering then it was definitely risker to use this test.

@Testluv:Could you please help us in tackling such questions[/spoiler]
Complete the passage questions are like inference questions. You will most likely have to put in the correct conclusion or else (as here) a correct piece of evidence that would logically support the conclusion. As with other inference questions, the best approach is to follow the gist of the passage, make a deduction and scan for a match.

Here, the author is arguing that the scan will obviate the need for surgeons to perform unnecessary appendectomies. Really? Let's examine what we have learned about the scan: the misdiagnosis rate is 2%. But are the misdiagnoses false positives or false negatives? A false positive is where the scan says you have appendictis when you don't while a false negative is when the scan fails to pick up that a patient has appendictis when in fact they do. False positives are not risky here b/c if a person who doesn't have appendictis gets his/her appendix removed, its no big deal. On the other hand, false negatives are very risky b/c if a person who has appendicitis doesn't get his/her appendix removed, then they may die. So, in order for the author's conclusion to be correct, the kind of misdiagnoses the scan makes must be false positives and not false negatives. That would be the piece of evidence that would support the conclusion (we know we want to put in some evidence here b/c the passage ends with "since'). That is our deduction, and now we scan for a match....choice B.
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