A comparison of the output of two spinning mills that produce woolen yarn—the Costello Mill and the Moorhead Mill—showed that...
GMAT Critical Reasoning : (CR) Questions
A comparison of the output of two spinning mills that produce woolen yarn—the Costello Mill and the Moorhead Mill—showed that the yarn from the Costello Mill had fewer flaws and greater strength. Since the Costello Mill's process differs from the Moorhead Mill's only in the way that the raw wool is treated before spinning, the treatment that the Costello Mill uses must be responsible for the superiority of its yarn.
The reasoning above assumes which of the following?
Passage Analysis:
| Text from Passage | Analysis |
| A comparison of the output of two spinning mills that produce woolen yarn—the Costello Mill and the Moorhead Mill—showed that the yarn from the Costello Mill had fewer flaws and greater strength. |
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| Since the Costello Mill's process differs from the Moorhead Mill's only in the way that the raw wool is treated before spinning, the treatment that the Costello Mill uses must be responsible for the superiority of its yarn. |
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Argument Flow:
The argument starts with evidence showing Costello Mill makes better yarn than Moorhead Mill. Then it identifies that the only process difference is how they treat raw wool before spinning. Finally, it concludes this treatment difference must be what causes the quality difference.
Main Conclusion:
The special wool treatment that Costello Mill uses must be what makes their yarn superior to Moorhead Mill's yarn.
Logical Structure:
This is a causal argument that uses elimination reasoning. The logic goes: Costello makes better yarn → only one process differs → that difference must cause the better results. The argument assumes no other factors could explain the quality difference.
Prethinking:
Question type:
Assumption - We need to find what the author must believe to be true for their conclusion to hold
Precision of Claims
The author makes a very specific causal claim: that wool treatment is THE cause of yarn quality difference, based on it being the ONLY process difference
Strategy
Look for ways the conclusion could fall apart even if we accept the facts. The author concludes that since wool treatment is the only process difference, it must cause the quality difference. What gaps exist in this reasoning? We need to find assumptions that, if false, would make the conclusion invalid while keeping the given facts intact.
This states that Moorhead's raw wool is at least as well-suited as Costello's for producing quality yarn. This is a necessary assumption because if Moorhead started with significantly inferior raw wool, then Costello's better results might be due to better starting materials rather than better treatment methods. The author's conclusion that treatment differences cause the quality differences would fall apart if the raw materials themselves were dramatically different in quality. For the argument to work, we must assume comparable starting materials.
This says that strength and freedom from flaws aren't the only properties for judging yarn quality. However, the argument doesn't assume this at all. The author is perfectly fine using just these two measures to demonstrate Costello's superiority. The argument doesn't need there to be other quality measures - it just needs these two to be valid indicators, which they appear to be.
This claims both mills target the same market and price range. But this is irrelevant to the author's causal argument. Whether the yarns are intended for luxury markets or budget markets doesn't affect whether the treatment difference causes the quality difference. The argument is about what causes better performance on objective measures (fewer flaws, greater strength), not about market positioning.
This suggests Costello's treatment isn't more expensive than Moorhead's. Cost considerations are completely outside the scope of this argument. The author is making a causal claim about what produces better quality, not an economic argument about cost-effectiveness. Whether Costello's method costs more or less is irrelevant to whether it causes better results.
This states that Moorhead doesn't have significantly larger annual output than Costello. Output volume has no bearing on the quality comparison or the causal conclusion. Whether a mill produces 1000 yards or 10000 yards annually doesn't change the fact that we can compare the quality of their respective products and identify what causes quality differences.