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#17 - We can be sure that at least some halogen lamps are

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Complete Question Explanation

Parallel Reasoning—SN. The correct answer choice is (B)

This question is difficult for many students, because sorting among the similarly-worded answer choices requires close attention to the detail of the language in the stimulus. The stimulus itself, however, is fairly straightforward, other than its order of presentation, which begins with the conclusion in the first sentence. There are three parts to this argument: a conditional rule; a fact that invokes the rule’s sufficient condition; and the conclusion, which satisfies the necessary condition.

Although the stimulus begins with the conclusion in the first sentence, we begin our analysis by looking at the last sentence, which provides the conditional rule: any item on display at Furniture Labyrinth is well crafted.

    display at Furniture Labyrinthitem ..... :arrow: ..... well crafteditem

Next, you are told that halogen lamps from most major manufacturers are on display at Furniture Labyrinth. This fact invokes the sufficient condition of our rule. Because we used “item” as a subscript when we diagrammed the rule above, we can simply replace “item” with “halogen lamps from most major manufacturers,” abbreviated as “HL”:

    display at Furniture LabyrinthHL

The stimulus author applies the conditional rule to this information about halogen lamps to reach the conclusion that we can be sure that at least some halogen lamps are well crafted, truncated as “some HL”

    display at Furniture LabyrinthHL ..... :arrow: ..... well craftedsome HL

Your prephrase in this Parallel Reasoning question is that the stimulus argument applied a conditional rule to a single statement of fact to derive a valid, limited conclusion about “some” of a type of item (i.e., at least some halogen lamps are well crafted).

Answer choice (A): The most efficient way to eliminate this answer choice is to recognize that its predictive conclusion, that “the temperature will drop abruptly on at least one day this week,” does not match the conclusion, which had to do with a current state of affairs, i.e., at least some halogen lamps are well crafted.

Answer choice (B): This is the correct answer choice. This answer choice presents a conditional rule, presents evidence that invokes the sufficient condition of that rule, and then concludes that since the sufficient condition has been satisfied, then the necessary condition must have been satisfied as well. In the argument breakdown provided below, the subscript “it” is used to replace the indefinite pronoun “everything.” Reordered for clarity, the argument proceeds:

    Premise: ..... everything Melinda writes is disturbing

    ..... ..... Melinda writesit ..... :arrow: ..... disturbingit

    Premise: ..... Melinda has written several different kinds of sonnets

    ..... ..... Melinda writessonnets ..... :arrow:

    Conclusion: we can be positive that there are at least a few disturbing sonnets

    ..... ..... disturbingat least a few sonnets

Answer choice (C): As with answer choice (A), the conclusion to this answer choice is a prediction regarding the future, rather than a description of present conditions.

Answer choice (D): This answer choice is incorrect, because the evidence presented does not satisfy the sufficient condition of the rule applied to reach the conclusion. The sufficient condition was “every lake nearby,” meaning that if it is a lake nearby, then it is teaming with healthy fish. This rule does not imply that every fish in every nearby lake is healthy. The conclusion to this answer choice, that at least some minnows are healthy, results from the application of a rule, not actually provided, that would state: if it is a fish in a nearby lake, then it is a healthy fish.

Answer choice (E): This is an attractive, incorrect answer choice that relies on a very subtle distinction between the conclusion in the stimulus and the conclusion in the answer choice. In the stimulus, the conclusion was that “at least some” halogen lamps are well crafted. Similarly, in answer choice (B), the conclusion was that there are “at least a few” disturbing sonnets. In this answer choice, however, the conclusion is that the cornmeal used is healthful and organic. In order to match the stimulus, this answer choice should have stated something like “at least some of the cornmeal used at Matteo’s Trattoria is healthful and organic.” Such language would better match the language in the stimulus, in which the conclusion was that at least some of one possible type of thing had the relevant characteristic (i.e., at least some of one type of item on display at the Furniture Labyrinth were well crafted).
Arindom
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Hi,

I diagrammed this as - HLFMM - Halogen lamps from major manufacturers; DFL - Display at Furniture Lab; WC - Well crafted

HLFMM :arrow: DFL
DFL :arrow: WC
-----------------------
C: HL :some: WC

I was between ans choice B and D because I wasn't sure how I could diagram it. Upon reflection, I see D is incorrect because "many" is treated as "some", right? And it would not reflect the same reasoning structure -

SM some LN
LN ---THF
------------------------
C: SM some HF

Is this correct? How would we diagram ans. choice B - specifically the first premise (Melinda has written several kinds of sonnets).

Thanks.

- Arindom
Nikki Siclunov
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Arindom,

Your understanding of the argument contained in the stimulus is spot-on. The only thing I would change is how I understand the statement, "halogen lamps from most major manufacturers are on display at Furniture Lab." What is the relationship between halogen lamps and Furniture Lab? Are all (or even most) halogen lamps in the world displayed there? No. Some, however, are. So, I'd simplify the original argument as follows:

    Premise (1) + (2): HL :some: Furniture Lab :arrow: Well Crafted

    Conclusion: HL :some: Well Crafted

The argument is deductively valid. Answer choice (B) parallels this structure perfectly. If Melinda has written several different kinds of sonnets, we can simplify this statement saying that she has written some sonnets:

    Premise (1) + (2): Sonnets :some: Melinda :arrow: Disturbing

    Conclusion: Sonnets :some: Disturbing

Answer choice (D) is incorrect because we don't know if every fish in the nearby lakes is healthy. All we know is that every lake is teeming with healthy fish: there is a big difference there, making answer choice (D) deductively invalid. Maybe some fish in the nearby lakes are healthy, and there are minnows among the fish in these lakes, but it's entirely possible that none of the minnows are healthy.

Hope this clears things up! :)
Nikki Siclunov
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Arindom
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Many thanks, Nikki! Makes more sense.

- Arindom
lsat2016
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Nikki Siclunov wrote:
Answer choice (D) is incorrect because we don't know if every fish in the nearby lakes is healthy. All we know is that every lake is teeming with healthy fish: there is a big difference there, making answer choice (D) deductively invalid.


Hello,

I think a consistent question that I have is whether to know when to diagram sentences. Could you explain when a sentence can be expressed as a conditional statement and when you can't? For example, although I see your reasoning for D, I still don't understand why the sentence can't be expressed as

every lake :some: healthy fish.

Doesn't the sentence say that there's AT LEAST ONE healthy fish in the lake? I wasn't 100% sure what "teeming" meant so I looked it up and it says "be full or swarming with"

Thank you so much! :)
Dave Killoran
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Hey LSAT,

Thanks for the question! Your question is one that I get frequently, and so I wrote an article about bit that might help! It's at LSAT Conditional Reasoning: When To Diagram.

A huge number of sentences on the LSAT (and indeed, in real life) can be expressed in conditional or formal logic terms. But the vast majority of them don't need to be diagrammed and shouldn't be diagrammed. The basic rule I discuss in the article linked above is: Diagram when you think it will help you better understand what the author is saying. What that means is that just because a sentence can be diagrammed doesn't mean you should diagram it. For example, your understanding of the lake/healthy fish relationship is perfect, and you probably don't need the diagram to understand that relationship.

So, usually when I see a conditional relationship on the LSAT, I don't worry about diagramming and I just try to make sure I understand what is being said. The one exception to that is if I see a stimulus that seems chock full of "some," "most," and "all/none" terms, because then I know they are throwing a Formal Logic question at me, and it will be easier to just write it down as I go.

Please let me know if that helps. Thanks!
Dave Killoran
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lsat2016
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Hello,

Thank you for your response! However, my specific question was regarding Nikki's statement that D is deductively invalid. What does this mean and does this mean that it can't be diagrammed?

Thank you!
Dave Killoran
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Oh, sorry! I was responding to this question I thought you were posing: "I think a consistent question that I have is whether to know when to diagram sentences. Could you explain when a sentence can be expressed as a conditional statement and when you can't?"

In simple terms, deductively invalid means that you can't draw that conclusion. The problem in (D) isn't about diagramming; it's about whether (D) has the same deductively valid structure as the stimulus. It doesn't. The stimulus appears as:


    Premise (1) + (2): HL :some: Furniture Lab :arrow: Well Crafted

    Conclusion: HL :some: Well Crafted (Valid)

In the argument above, the two premises prove the conclusion, meaning that the conclusion can be validly drawn.

In comparison, answer choice (D) appears as:


    Premise (1) + (2): Minnows :some: Lake :some: Healthy

    Conclusion: Minnow :some: Healthy (Invalid)

The formation of two "somes" in succession does not allow for a valid conclusion. And, as you can see, it doesn't mean that it can't be diagrammed, just that the diagram doesn't yield a conclusion that is effectively supported.

Please let me know if that helps. Thanks!
Dave Killoran
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15veries
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So most=some here?
most major...=there are others too and most major is just part of it?
Last edited by 15veries on Tue Oct 11, 2016 5:48 am, edited 1 time in total.
Jonathan Evans
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Hi, 15veries, I'm sorry but could you please elaborate on your question? The stimulus states "We can be sure that at least some halogen lamps are...", as noted in the title to this thread. Was there some other aspect of this question you are having trouble with?