Appendicitis (inflammation of the appendix) is potentially fatal; consequently, patients with symptoms strongly suggesting appendicitis almost always ...
GMAT Critical Reasoning : (CR) Questions
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 _____
Which of the following most logically completes the passage?
Passage Analysis:
| Text from Passage | Analysis |
| Appendicitis (inflammation of the appendix) is potentially fatal; consequently, patients with symptoms strongly suggesting appendicitis almost always have their appendix removed. |
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| The appropriate surgery is low-risk but performed unnecessarily in about 20 percent of all cases. |
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| A newly developed internal scan for appendicitis is highly accurate, producing two misdiagnoses for every 98 correct diagnoses. |
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| Which of the following most logically completes the passage? Clearly, using this test, doctors can largely avoid unnecessary removals of the appendix without, however, performing any fewer necessary ones than before, since ______. |
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Argument Flow:
The passage starts by explaining the current medical dilemma: appendicitis is dangerous so doctors err on the side of caution, but this leads to 20% unnecessary surgeries. Then it introduces a highly accurate new scan as a potential solution. Finally, it asks us to complete the logic for why this scan solves the problem.
Main Conclusion:
The new scan can help doctors avoid unnecessary appendix removals while still catching all the cases that truly need surgery.
Logical Structure:
The argument connects the scan's high accuracy (98% correct) to solving the current problem of too many unnecessary surgeries (20% error rate). We need to find the missing piece that explains why accuracy helps avoid unnecessary surgeries without missing necessary ones.
Prethinking:
Question type:
Logically Completes - We need to find the missing piece of reasoning that explains why the new scan allows doctors to avoid unnecessary surgeries without missing necessary ones.
Precision of Claims
The key claims involve specific accuracy rates (98% correct, 2% misdiagnosis) and current unnecessary surgery rates (20%). We need to connect these numbers to show how the scan solves the problem.
Strategy
For logically completes questions, we need to find what missing information would make the conclusion follow logically from the premises. The argument claims the scan helps avoid unnecessary removals without missing necessary ones. We need to identify what about the scan's accuracy makes this possible - specifically, we need to understand what types of errors the scan makes and how those errors relate to the desired outcome.
This choice talks about the severity of other medical conditions that patients might have instead of appendicitis. While it's nice to know that misdiagnosed patients have less serious conditions, this doesn't explain how the scan helps avoid unnecessary surgeries without missing necessary ones. The severity of alternative conditions is irrelevant to the scan's ability to accurately identify appendicitis cases. This choice doesn't address the core logical gap about what types of errors the scan makes.
This choice directly addresses the type of errors the scan makes - specifically that all misdiagnoses are false positives (saying someone has appendicitis when they don't). This is exactly what we need to complete the logic. If the scan only makes false positive errors, then it will never miss a real case of appendicitis (no false negatives), ensuring all necessary surgeries happen. Meanwhile, the 98% accuracy means most people without appendicitis will be correctly identified, avoiding unnecessary surgeries for them. The 2% who get false positives will have unnecessary surgery, but this is much better than the current 20% unnecessary surgery rate. This perfectly explains how the scan achieves both goals.
This choice claims that everyone diagnosed with appendicitis actually has it (no false positives). While this would eliminate unnecessary surgeries for those testing positive, it doesn't account for the 2% error rate the passage mentions. If there are no false positives, then the 2% errors must be false negatives, meaning some people with real appendicitis wouldn't be diagnosed. This would contradict the claim that we'd perform just as many necessary surgeries as before.
This choice discusses patients having multiple symptoms, but symptom quantity doesn't relate to the scan's accuracy or how it helps achieve the stated goals. Whether someone has one symptom or several doesn't explain how the scan avoids unnecessary surgeries while catching necessary ones. This is irrelevant information that doesn't complete the logical argument.
This choice suggests that misdiagnosed patients lack certain symptoms, but this doesn't clarify whether the misdiagnoses are false positives or false negatives. Without knowing the direction of the errors, we can't determine how the scan helps achieve both goals. Additionally, focusing on symptom presence in misdiagnosed cases doesn't directly address the core issue of unnecessary vs. necessary surgeries.