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I found this one very tricky.
As for AC A, I think I understand that AC A meets the target by introducing a third party, stress, that could be responsible for causing both snoring and smoking. However, I am wondering that what if stress indeed causes both snoring and smoking, and at the same time, smoking causes snoring. A third party cannot exclude the possibility that smoking doesn't cause snoring.
As for AC D, I understand that it indeed doesn't infer any hard causation. But I think it is a quite soft one. The more cases are, the better chance that smoking causes snoring. I think in scientific research, it is indeed has such inference?
Could someone help me with this confusion? Thank you!
Admin Note: Edited title. Please use the format: "PT#.S#.Q# - brief description of question
Comments
@AlaiaSun Anytime you see a Logical Reasoning question imply that correlation is actually causation, you should IMMEDIATELY be suspicious! If X and Y are correlated, we are left with three possibilities:
1) That X causes Y
2) That Y causes X
3) That Z causes X and Y
Without more information, we cannot draw ANY conclusion! 1, 2, and 3 are all equally likely. We should immediately be looking for answer choices that point us to one of those 3 possibilities.
Answer choice A points us toward possibility 3. In fact, it definitively proves 3, at least for certain individuals. As you point out, the answer choice provides us with a third party ("Z") that causes both snoring (X) and smoking (Y). That casts doubt on the conclusion reached in the passage by provided an alternative explanation.
Note that for weakening questions, the answer choice doesn't have to absolutely REFUTE the argument. As you note, it could still be possible that Z causes Y which causes X. However, it does cast doubt on the conclusion. Before, there was a 1 in 3 chance that the author picked the right possibility. Now we are looking at a much lower chance - and one for which we have no hard evidence.
In contrast, (D) really gives us nothing. It doesn't give us any indication of which of the 3 possibilities is more likely. In fact, it simply restates a fact given in the stimulus, "...snoring, though not common in either group, is more common among smokers..." A fact given in the argument stimulus cannot weaken the argument.
Hope that helps! Let me know if I can explain it more clearly!
Best,
Scott
When I read through AC D one thing that immediately stuck out for me was that it basically repeats information to us that we already know from the stimulus. Compare AC D to the first sentence. If we know that snoring isn't common in either group then of course most smokers don't snore.
Most is a range that's larger than half. E.g., saying most smokers don't snore is consistent with 49 out of 100 smokers snoring. To use a slightly more intuitive example, say 49 out of every 100 smokers get lung cancer and only one out of every 100 nonsmokers get lung cancer. If I proposed that there's a causal link between smoking and lung cancer, it wouldn't be very compelling to argue that most smokers don't get lung cancer. My proposal would still stand.
Remember when you're reading through these ACs that they are to be understood as being true. So if it's true that stress can induce both snoring and smoking in certain individuals then the author's hypothesis that smoking by itself can induce snoring is called into question. We now have the possibility of another outside causal force causing both. Don't overthink these and rationalize yourself out of the correct AC. We're being asked to weaken the argument not completely disprove it.