#6 - While grapefruit juice is a healthy drink, it has been

[Administrator]

Complete Question Explanation

Weaken. The correct answer choice is (A).

The argument gives us three premises: 1) Grapefruit juice boosts the performance of some medicines; 2) the wrong dose of medicine can be dangerous; 3) taking the lowest effective dose is best. Based on these premises, the author concludes that the best course of action would be to take lower doses of the medicine, plus a prescribed amount of grapefruit juice (presumably to boost the medicine to an effective level). The stem asks us to undermine that argument, which means we need new information in the correct answer that would raise some doubts about that practice (low does plus grapefruit juice) being the best choice.

A broad prephrase here would be good, something like "there is some problem with taking grapefruit juice with these medicines" or "another option might be better." No need to get more specific than that or to pinpoint what the exact problem would be. All we have to do is raise doubts about this being the best approach, so ANY problem with the approach or possible better alternative should do the trick.

Answer choice (A): This is the correct answer choice. Here we are presented with a potential problem with the suggested approach. If the amount of the chemical in grapefruit juice is unpredictable, we might boost the medicine too much, or too little. Prescribed amounts of juice would have varying levels of the chemical and thus potentially varying levels of effect. Not what you want from your medicine!

Answer choice (B): If grapefruit juice is less expensive than the medicine, then this approach is not only potentially better for medical reasons, but also for economic reasons. That makes this answer a Strengthener, the opposite of what we want.

Answer choice (C): This answer has no effect on the argument. We already knew that it was the chemical in the juice, rather than the juice itself, that had the effect, so it's not really new information that removing the chemical (the cause) leads to elimination of the effect.

Answer choice (D): While this answer is very informative and may help us to better understand how and why the effect occurs, it does nothing to undermine the suggested practice. Your reaction to this answer should be "that's fascinating, but that's not a problem."

Answer choice (E): Pointing to the past practices of doctors who didn't know about the chemical does nothing to weaken the claim about the suggested practice. It may be that at some point doctors saw grapefruit juice as a problem, but the proposal is based on having better information now, and those past practices should not raise any doubts about the new proposal.

[mokkyukkyu]

Hi, I'm not sure why A is the correct one...
It says glass to glass, but wouldn't it contain the same amount of chemicals if the amount of the juice is the same??

[Nikki Siclunov]

Not necessarily. If answer choice (A) is true, and the amount of the chemical in grapefruit juice is highly unpredictable from glass to glass, then it would be impossible to measure by how much to lower the prescribed dose of medicine in order to reach the desired effective dose.

A word of caution: Don't question the answer choices - when attacking a Weaken question, you are required to assume that each answer choice is a true statement of fact, and examine its implications on the argument's conclusion. Furthermore, there is nothing implausible about answer choice (A): maybe some types of grapefruit juice have more of this chemical than other types? Or maybe freshly squeezed juice has a different chemical concentration than pasteurized juice? Clearly, there is a potential for variability here, which can be a problem if we are to adopt the recommendation offered in the stimulus.

Hope this clears it up!

Thanks,

[T.B.Justin]

I have a couple of questions; the structure of the argument and the reason answer choice (C) is incorrect.

For the argument:

I loosely identified two premises and a conclusion, I wonder if perhaps its more appropriate as an intermediary conclusion, premise, and conclusion.

Since it is always desirable to take the lowest effective dose, for the reason that (for this reason) getting the wrong dose is dangerous, therefore the best medical approach would be to take lower doses of these medicines along with prescribed amounts of grapefruit juice.

For the incorrect answer choice (C):

I found this to be incorrect because the argument is about the affect of grapefruit juice, and if the chemical that causes the increased effectiveness of certain medicines is removed, then I think that has no impact on this argument.

[Brook Miscoski]

TB Justin,

Unless you are doing an argument parts question--and even then--it is usually unnecessary to think about whether something is a pure premise or an intermediate conclusion. In this case, there is no intermediate conclusion, because "lowest effective dose" and "wrong dose dangerous" are independent considerations, the one is not derived from the other. The considerations are that getting the wrong dose could harm the patient and that lowering the required dose could help the patient. With that in mind, you're to weaken the proposed conclusion--that drinking grapefruit juice to lower the required dose is a good idea. (A) indicates that since the chemical in grapefruit juice is unpredictable, you could get the wrong dose, making it a bad idea.

[T.B.Justin]

Hey Brook,

When I break down a stimulus it helps me see which statements support each other, and that helps me more effectively identify any gaps to shore up or undergird. Its necessary for my thought process, at the moment, to feel the flow of an argument, what the task of the stem is and move forward accordingly. Nonetheless, I am always open to refining my process to become more efficient.

If there are two premises with independent thoughts of one another, although in this instance I think they are being used under the same general context, does that mean they cannot, in general, be a support for one or the other?

[Adam Tyson]

We aren't big fans here of coming up with broad, sweeping rules like "that cannot be the case", T.B., because the authors of this test are so good at coming up with exceptions to every rule (and sometimes it feels like they are watching this forum, listening to our webinars and podcasts, and then creating new content just to foil us!) So, I will say that when two premises come from two totally different ideas, they will PROBABLY not be supporting each other, but instead will independently support the conclusion, like the legs of a table. If I have a premise that Mary Jones is very popular in her district, and also that she is really good at hacking voting machines, and then conclude that she is likely to be declared the winner in her upcoming election, those two premises don't have anything to do with each other and do not support each other. On the other hand, if I say she is very popular, and she has done a great job at encouraging voter turnout, so she will likely be the winner, those premises might be seen as somehow connected. Maybe she encouraged turnout because she is popular? Maybe she is popular because she encouraged turnout? Or perhaps the two premises are completely unrelated - her popularity and her success at getting out the vote may be totally independent premises.

The point, I think, is that we don't need to tease out those relationships, unless the stem tasks us to do so (as it does in Method-AP questions and Main Point questions). If it helps you to better grasp the structure of the argument, and thus better prephrase and sort answer choices, great! But don't let that process get in the way of the real task at hand, which is to prephrase, sort, and select the best answer from among the five choices. When the process supports the goal, go with it, but when it takes priority over the goal, you're going to find yourself wasting time and effort. That's what I think Brook was warning you against.

[T.B.Justin]

Hey Adam,

Thanks for the insight. I haven't quite figured out how to stay more on course in LR in order to not waste time and effort. Its actually pretty frustrating. I get caught up going over the stimulus with a microscope and I admit it feels counter-productive at the end of a section and I am leaving around 5-8 questions unattempted, but I am usually around 70-80% effective in the ones I do attempt, so I am happy with that effectivity yet frustrated that I am leaving opportunity to spread that to the ones I am not getting to, which in my opinion is like leaving food on the table and I am so hungry for it but I am having trouble figuring out how to get to it!

[cmnoury1221]

Hello,

For this question I was between answer choices A and C; Is C wrong because it does not consider the conclusion but a premise of the stimulus? I took the conclusion to be, "Getting the wrong dose is dangerous. Since it is always desirable... the best medical approach would be to take lower doses of these medicines..."

Thanks,
Carolyn

[KelseyWoods]

Hi Carolyn!

You can be a little more precise with your identification of the conclusion. "Since" is a premise indicator and when you have that term, the half of the sentence modified by "since" is a premise supporting the other half of the sentence. So "Getting the wrong does is dangerous" and "it is always desirable to take the lowest effective dose" are premises to support the conclusion that "the best medical approach would be to take lower doses of these medicines along with prescribed amounts of grapefruit juice."

In Weaken questions, we are trying to attack the argument by adding additional information to show that the premises stated do not necessarily equal the conclusion stated. So it is always important to focus on that conclusion.

Answer choice (A) weakens the conclusion of the argument by telling us that the amount of the chemical in grapefruit juice is unpredictable. If this is true, it attacks the argument that the best medical approach would be to take lower doses of these medicines along with prescribed amounts of grapefruit juice: if you can't predict how much chemical is in the grapefruit juice, you wouldn't be able to prescribe certain amounts that would keep the doses of medicine consistent, which would make it not a very good medical approach.

Answer choice (C) strengthens the idea that the chemical in grapefruit juice is what affects how the medicines are absorbed. If you remove the cause (the chemical) it removes the effect (the change in how medicines are absorbed), thus it strengthens the causal relationship between the chemical in grapefruit juice and the effect it has on how certain medicines are absorbed. As you said, this answer choice only involves a premise. And in fact, it strengthens that premise. So it has nothing to do with weakening the conclusion.

When we are trying to weaken (or strengthen) and argument, we need to focus on the conclusion and how the conclusion is connected to those premises. You don't want an answer choice that only weakens (or strengthens) a premise--it needs to weaken (or strengthen) how the conclusion follows from those premises. Also, always make sure to be clear on whether you are weakening or strengthening as they will often include answer choices which do the opposite of what you're being asked to do.

Hope this helps!

Best,
Kelsey