Q5 - A recent study showed that

[aznriceboi17]

I was initially attracted by choice A. The suggestion I see is that regular exercise would contribute to the development of arthritis, in which case we'd expect that regular exercisers are overrepresented in the population of people who drink 3 cups of decaffeinated coffee per day. This would then inflate the occurrence of arthritis among this group compared to its occurrence in the general population (which admittedly doesn't offer a direct comparison to the population of people who drink 3 cups of regular coffee per day).

Is this the wrong way to be thinking about this problem?

[tian.application]

I was trapped by A when I was doing my timed PT yesterday.

I had the same logic as you did but I think the key is here that we were both making a unwarranted logic leap here. Exercise regularly does not necessarily lead to arthritis (maybe decrease the frequency!). So A is kind of irrelevant.

While C proposed an alternative to weaken the argument (relevant to evaluate the conclusion)

[tommywallach]

Hey Guys,

Well, I see the appeal of (A) for sure (by the way, Tian, I'm sure Azn was assuming exercise was good for the body, not bad!).

Let's look at the core:

Premise: People who drink three cups of decaf are more likely to get arthritis than those who drink three cups of regular.

Conclusion: Decaf coffee contains something that damages connective tissue and isn't present in regular coffee.

The problem is that the argument goes to "damage" of tissue, as opposed to "protection" of tissue. (You could also argue causation vs. correlation, but the answers choose not to explore that issue.)

(A) The problem is that it says "beverages," rather than "coffee." Imagine we had an answer to that issue: "Yes, people who exercise regularly are more likely to drink decaf beverages." We'd still have to find out if that connects to coffee. It could be tea or soda.

(B) We already know this is about people who drink three cups.

(C) CORRECT. Aha! Could be that regular coffee protects, as opposed to decaf doing damage.

(D) Again, we already know it's about people who drink three cups.

(E) Again, this may or may not be true, but it wouldn't change what we know about people who do drink coffee.

Hope that helps!

-t

[shiqi0628]

Hi tommy

i think the beverage part is a little bit tooo detail creep for NO.5 i think its because the comparison is btw decaffeinated coffee drinker and people who dont..it should be compare with peoplewho drink regular coffee...thats how i cope with during timed prep..
am i justified in doing that..?

[mchelle]

I wanted to add my thoughts on this question since I also incorrectly chose A. In reviewing the answers, I initially analayzed A as incorrect since it brings in the concept of exercise which seems out of scope and doesn't quite get at the decaf-connective tissue connection. But upon closer inspection of my original thought process, I think I understand better why I chose A over C, and why A is wrong.
I did not take into account the implication of the study's design: it compares a group of decaf coffee drinkers to a group of regular coffee drinkers. There is no control group in this study, so we can't attribute the higher incidence of arthritis among decaf coffee drinkers to something in decaf coffee. The lack of a control group may seem obvious, but it is important and helps explain why regular coffee consumption could alternatively protect connective tissue instead of decaf damaging tissue. The study essentially compares two groups with different conditions, as opposed to one with X and one without X, and then makes the unwarranted conclusion that X1 (Decaf) must explain the variation in result. This is what answer choice C gets at: it's possible that X2 (regular coffee) could also explain this variation, since no control group was measured.
When I originally took this prep test, I chose A because I thought that it could provide an alternative explanation for the presumed connection between decaf coffee and arthritis. At the time I did not take into account that the study omitted a control group, so I didn't quite fully understand the significance of C. Perhaps, had the study only measured a group of decaf drinkers and a group of non-decaf (and non-regular coffee) drinkers, A may have been more relevant.

[WaltGrace1983]

I realized that I could have read this one a lot more efficiently by thinking about "decaffeinated coffee" as simply "~caffeine coffee." When I thought about it in this way, the question actually became a lot more simple for me to think through, strange but true. The question goes as follows...

3 cups of ~(caffeine coffee) = twice as likely to develop arthritis in comparison to 3 cups of (caffeine coffee).
→
~(caffeine coffee) = contains something that is both unique to ~(caffeine coffee) and damages connective tissue

Our goal is to find something that would be useful to determining the validity of this argument. This seems like a straightforward correlation/causation problem so I am thinking about things that people who drink ~(caffeine coffee) could do that would make them more prone to damaging connective tissue. That was the first thought anyway.

(A) The problem here is that we don't know what exercise has to do with arthritis. It is very hard not to apply what we think we know about the connection here and just go with only the information provided. If there had been something about exercise in the stimulus, then perhaps we could have inferred something. However, as (A) stands we just cannot jump to conclusions (though I did, quite wrongly).

(B) What does this have to do with arthritis? We have to show how ~(caffeine) contributes to a higher rate of arthritis.

(C) This is by far the most direct as it deals directly with the "degeneration of connective tissue," the cause of arthritis. I'll keep it for now and move on.


(D) We still need to know something about what kinds of coffee they drink and how that impacts arthritis. If this answer had said something like "whether most decaffeinated coffee drinkers do exercise X that has been shown to cause arthritis," then we would have a much better answer.

(E) I don't think this one should be written off as easily as it has been and here's why: this deals directly with the correlation/causation issue. if we know that people with arthritis are more/less likely to drink a certain type of coffee, then I think we can more classically address the correlation/causation issue. The problem with (E), however, is that it just talks about coffee in general. We want to know about a specific type of coffee, either (caffeine coffee) or ~(caffeine coffee).

Had (E) said, "whether people who have arthritis are less likely to drink decaf coffee," then I think you can make an argument that this would be correct. If we know that more people with arthritis drink decaf coffee, then perhaps the cause of the arthritis has nothing to do with the contents of the decaf coffee, perhaps it just so happens that people with arthritis like decaf coffee.

Now this would still prompt us to ask more questions about the causation of the arthritis - this modified (E) would still not validate/invalidate the idea that the decaf coffee caused the arthritis. However, I am just trying to say that (E) is trickier than I think we have given it credit for.

So here is a shorter version of what I was trying to say: the correct answer had to deal specifically with ONE type of coffee (regular or decaf) and it had to connect itself to the idea of ARTHRITIS. The rest of the answer choices are wrong because they fail to do one or both.

(C) is correct (to my dismay). It deals directly with arthritis AND decaf coffee, the two critical elements we needed.

Now in order to validate the argument's conclusion, we would have to show that both things occurred (damages & unique); to invalidate the conclusion, we could show that one thing failed to occur (~damages or ~unique).

If we know (C), then maybe we could say that caffeine coffee doesn't actually damage. Instead it slows the naturally occurring damage. Or, on the other hand, we could show that caffeine coffee doesn't slow anything and perhaps it would make sense that decaf damages.

Hope that helps. This question sucked - especially for #5 but I think the main thing to do is to not make unwarranted assumptions.

[jm.kahn]

There have been some reasons mentioned above as to why A is not credited, but none of them is convincing in that A clearly shows a correlation between decaf drinkers and exercise that doesn't exist in regular coffee drinkers and exercise which can be helpful in evaluating the conclusion.

The reason given by tommywallach about A is wrong because of "beverages" instead of "coffee" is actually very weak like one poster above mentioned. If there is no reason to think that A could be useful to evaluate, then there is no reason to think that A that had "coffee" instead of "beverages" will be useful to evaluate. The reason has to be something else. I can see why C is clearly the best choice, but A has to be wrong for a solid reason. Can an LSAT expert give a solid clear reason for why it's wrong?

[Fazzvm56]

I initially picked A as well, but upon reviewing the question I picked C and I think I understand why A is wrong and C is right. The question is asking "Which one of the following would be most useful to know in order to evaluate the journalist's argument?"
The argument is talking about decaf coffee, regular coffee, and damaging connective tissue. I think when picking A I was thinking, as many other people were probably thinking as well, that we were looking for something that added to the argument in another way - like something that could be a third-party variable that influences these things. But the question should be looked at in a way that helps you evaluate the three things the argument is discussing, not bring in a fourth thing that could possibly influence it.

That's exactly what A is doing - it is bringing in another variable that could affect decaf coffee and indirectly damaging connective tissue. But would exercising really be useful to this question? Even if people who exercise more regularly are more likely to drink decaf coffee - what does that really tell us? Not much... maybe that it could be the thing actually causing the damage to tissue or the thing that is leading these people to drink decaf coffee - but it really isn't telling us much at all besides that it is leading people that exercise to drink decaf coffee.

Whereas C is directly relating the variables mentioned in the argument. The argument is saying that decaf is somehow damaging connective tissue, while caffeinated is not. Answer choice C is saying that knowing whether the degeneration of connective tissue is slowed by consumption of caffeine and other stimulants would assist you in determining whether the argument is correct or not. In answering C with a yes or no answer:

Yes, caffeine slows the degeneration of connective tissue (and therefore non-caffeine/decaf does not)
this explains why people who drink decaf are twice as likely to develop arthritis/have damage to connective tissue.
No, caffeine does not slow the degeneration of connective tissue
then something else is wrong with the argument or theres another factor involved.

Regardless, answer choice C allows you to to evaluate the argument like the question is asking you to, while answer choice A is simply bringing another factor into the equation that doesn't really tell you much.

Hope this helps.

[erikwoodward10]

I think that the above poster nailed it.

I, like many, selected A. Through so many PTs I've conditioned myself to think that when I see correlation and read causation, I need to point that out. This is great for weakening/strengthening/assumptions/principle questions, but this is a unique stem: we're told to select something that sheds light on the identified connection between the premises and the conclusion. Therefore any outside info, I would argue, would immediately disqualify an answer choice. Even if we show that another element weakens the conclusion, that doesn't say anything about the relationship of the given premises to the stated conclusion. It just complicates things.

I see more modern LSATs getting trickier and more nuanced in how these types of common flaws are presented. Something to watch out for, and more reason to really understand the principles and logical foundations of the questions, and not just the correct answer!

[laura.bach]

Another thought on (A) (not to beat a dead horse here):

1. Even skipping the assumptions between "coffee" and "beverage" and "damage to connective tissue" and "exercise", and even if it was true that those who [exercise regularly] are more likely to [drink decaff beverages], (A) doesn't really provide an alternate cause.

(A) doesn't address either of the groups in question. Generally an alternate cause answer choice would start with the group in question and then state a behavior: "those who [drink 3 cups a day of decaff coffee] are more likely to [X]".

Note that (A) is not: Those who [drink 3 cups a day of decaff coffee] are more likely to [exercise regularly].

Instead, (A) states that out of 100 athletes, maybe 51 (or more) would drink decaff beverages, but gives us no indication as to, out of this group of 100 decaff drinkers, how many would be athletes.

In other words, even with the most generous of assumptions: everyone who exercises drinks only decaff (maybe they always drink less than 3 cups?) it's still possible not a single person in the study has ever exercised a day in their life.

2. Then, as stated before, even if you made the assumption that 100 decaff drinkers are more likely to exercise, there's the second leap between "regular exercise" and "damage to connective tissue"

3. And, as stated before, then a third leap between "decaff beverages" and "decaff coffee".

I think those 3 points together, coupled with the arguments for (C), make enough of a case against (A). There are simply too many unstated assumptions that need to be brought in. That means even if we knew the answer to (A) we couldn't evaluate the argument any better (without knowing the answer to several other questions anyway).