In tests for pironoma, a serious disease, a false positive result indicates that people have pironoma when, in fact, they do not; a false negative result indicates that people do not have pironoma when, in fact, they do. To detect pironoma most accurately, physicians should use the laboratory test that has the lowest proportion of false positive results.
Which of the following, if true, gives the most support to the recommendation above?
(A) The accepted treatment for pironoma does not have damaging side effects.
(B) The laboratory test that has the lowest proportion of false positive results causes the same minor side effects as do the other laboratory tests used to detect pironoma.
(C) In treating pironoma patients, it is essential to begin treatment as early as possible, since even a week of delay can result in loss of life.
(D) The proportion of inconclusive test results is equal for all laboratory tests used to detect pironoma.
(E) All laboratory tests to detect pironoma have the same proportion of false negative results.
This problem contains some great examples of one of the GMAT test writers' favorite tricks: answers that strengthen or weaken not the stated conclusion, but rather a related
conclusion. This is why it's so crucial to precisely identify the stated conclusion on strengthen / weaken questions!
Note that the full conclusion is
To detect pironoma most accurately, physicians should use the laboratory test that has the lowest proportion of false positive results.
We are trying to detect pironoma most accurately - we have no other
See any problems with this conclusion? To achieve the most accurate results, the conclusion says we should focus on minimizing false positives. But wait a minute, the passage discussed two
sources of inaccuracies in these tests - false positives and false negatives
. The conclusion does not address false negatives, so to strengthen we need a statement that does!
A) Side affects are certainly a real-world concern, but they are not discussed in the stated conclusion (or in the passage at all, for that matter!) Wrong.
B) Same problem as A). Wrong.
C) Again, early treatment is a real-world concern, but not a concern for this argument. Wrong.
D) Inconclusive results were not discussed as a source of inaccuracies in the passage. This is probably a mild strengthener, because it does eliminate one other concern (the conclusion narrows our concerns all the way down to just false positives). But since it does not address false negatives, we should be highly suspicious of this answer. Go ahead and read E), but this one is probably wrong.
E) Here we have our exact prediction. Correct.Takeaways:
[•] Carefully note the exact wording of the conclusion.
[•] Don't be tempted by logical answers that are out of scope for the given argument.
Mark Sullivan | Manhattan GMAT Instructor | Seattle, WA
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