LR Question 25 Explanation
QUESTION TEXT: Although wood-burning stoves are more efficient than…
QUESTION TYPE: Weaken
CONCLUSION: Wood-burning stoves are more dangerous that open fireplaces.
REASONING: Their smoke travels more slowly and therefore leaves behind more creosote. Creosote can clog up a chimney or burn inside of it.
ANALYSIS: This argument makes a common error: it lists one relevant difference and then makes a final judgment. We know one disadvantage of stoves. But it could be that fireplaces have other disadvantages that make them even more dangerous.
The correct answer lists one such disadvantage.
___________
- This sounds tempting but it doesn’t do much. The stimulus is talking about how dangerous the stoves are on average. It could be that the most efficient stove costs $1,000,000 and nobody owns one. That won’t affect the average stove.
- This makes sense – if you don’t use your stove, how can it produce creosote. But this affects both fireplaces and stoves.
- CORRECT. This shows a reason that fireplaces are dangerous. It might outweigh the creosote danger and it weakens the argument.
- That doesn’t matter since we know that stoves produce more creosote.
- But if they used them, which type would be more dangerous? This doesn’t let us conclude that fireplaces are as dangerous as stoves.
More Resources for Weaken Questions
- Intro Course lesson: This intro course lesson covers Weaken questions.
- Mastery Seminar lesson: This LR Mastery seminar lesson covers weaken questions.
I had rejected (C) and still don’t understand how it is correct. My reasoning was following:
If we say students in class A are smarter than students in class B. We mean that average level of smartness is higher in A than B, it doesn’t imply that every student in A is smarter than B.
If I think along same line for the given question and argument, wood burning stoves are more dangerous than open fireplaces, it should be on average level and it is possible that it is less dangerous “inside homes”. Thus, we can infer (C) and it doesn’t seem a new information to weaken the argument.
I had selected (B) as it says there is another factor apart from flame type which is not mentioned in the argument and contribute to the danger, thus, weakens the argument.
Please let me know where I am going wrong here.
I think your main error lies in how you’re interpreting what the conclusion is actually claiming.
The conclusion is not that wood-burning stoves are more dangerous in one specific respect (e.g. more dangerous for chimney fires). It’s that they’re more dangerous, overall. But the evidence only talks about one particular source of danger: creosote buildup and the risk of chimney fire.
Because of that, the argument is vulnerable to information showing that open fireplaces are more dangerous in some other important way.
That’s exactly what C does. It tells you that open fireplaces pose more risk of severe accidents inside the home than wood-burning stoves do. Once that is true, the original reasoning becomes much weaker, because you now have at least one significant category of danger in which open fireplaces are worse.
Your class analogy isn’t quite parallel. In that analogy, you’re assuming that the claim is explicitly about averages. But in this stimulus, the author never establishes anything like an overall assessment of all relevant risks. The author establishes only one specific risk and then uses that to justify an absolute comparative conclusion. Showing that wood-burning stoves have a higher risk in a different context is therefore new information, not something already built into the claim.
Another thing I don’t really understand from your reasoning is your differentiation of “inside the home” vs. not. The stimulus is saying “Wood-burning stoves -> more creosote -> more dangerous”. C is saying “Open fireplaces have a more risk of severe accidents”. While C specifies inside the home, the stimulus is also situated within the home (e.g. mentioning chimneys). Generally, wood-burning stoves and fireplaces are found within people’s home. So when you say “it should be on average level and it is possible that it is less dangerous inside homes” – if most relevant use occurs in homes, then a higher in-home accident risk necessarily affects any reasonable assessment of which option is more dangerous overall.
As for B, the argument never claims that the type of flame is the only factor affecting creosote. It only says that, compared to open flames, wood-burning stoves produce cooler smoke and therefore more creosote. As Graeme noted, B affects both the stoves and fireplaces. Sure, if you don’t use it, it probably won’t be dangerous (at least not due to creosote). But there’s nothing specific there telling us why open fireplaces may be more dangerous than wood-burning stoves, which is what we need. Note that we need to weaken the argument overall, and the main part of the argument is that stoves are more dangerous than fireplaces, which B doesn’t address at all.
TLDR: C weakens it because it introduces a countering source of danger that directly challenges the claim that stoves are more dangerous overall, which B doesn’t give us any specific information that would suggest that fireplaces are more dangerous than stoves.
Hope that helps! Let me know if you have further questions.