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NA Questions

TexAgAaronTexAgAaron Alum Member

I have been really struggling with NA questions and am working on understanding them better. I think I have figured something out but I want to confirm it.

When you do SA questions, we have to find the missing piece to make the argument valid. With NA questions we take the entire valid argument and accept the NA that come with it: [p1 + p2 = C] --> NA

So when I am looking at NA questions, do I accept the stimulus as a completed argument and am just looking for something an assumption that must be true/necessary? Almost like a MBT but I'm looking for something subtle?



  • jsfollowerjsfollower Member
    edited October 2017 66 karma

    I think there are some necessary assumption questions that require us to fill the gap. For example, there were occasions in which the correct answer to na question was both necessary and sufficient. Also, all of the logical reasoning questions with arguments in them are flawed. So, I think it’s safe not to assume the argument as complete/valid.

  • TexAgAaronTexAgAaron Alum Member
    1723 karma

    I see your point on the possible NA/SA answer choice. That is where I could see an invalid/incomplete argument and needing a bridge.

  • Heart Shaped BoxHeart Shaped Box Alum Member
    edited October 2017 2426 karma

    From my personal experience, I found it to be crucial to separate out the argument structure, namely premise and conclusion. The necessary assumption has be embedded in the relationship between the two. Don't be distracted by the context cuz that's where lots of trap ACs come from. (Don't ignore them either as they could be important to understand the argument structure) There are times I almost feel like that's part of the reason why the test writers write those convultated "useless" context -- to create trap ACs. So what I do is I separate out the structure and find the conclusion, then I ask myself why this is the confusion? Oh it's "bc" this and this (premise) 9 outta 10 if not all 10 times, i spot the NA there between the P and C relationship. It has to be if we really think about it.

    With the really short argument, one sentence premise therefore conclusion, be mindful of the AC that is both SA and NA.

    Last, be ruthless in eliminating the wrong ones. Have a general sense of the direction, again relationship between P and C (not necessarily a prephrase) The ones talking about something else is out immediately during the first round. Take a scan of all ACs first before diving into POE, normally you can spot the ones talking about the relationship between P and C, or at least just talking about P and C, start there.

  • Heart Shaped BoxHeart Shaped Box Alum Member
    2426 karma

    Oh and the argument def doesn't have to be valid, it could be a crapy argument, we just need to find the NA. All "arguments" (valid or crappy) have assumptions, at least on the LSAT.

  • TexAgAaronTexAgAaron Alum Member
    1723 karma

    Thank you @"Heart Shaped Box", that makes a lot of sense to me. I feel like I have been getting caught up in context a lot and it throws me off enough to get the question wrong. I appreciate the response!

  • joycool9567joycool9567 Alum Member
    133 karma

    I think there are definitely NA questions that asks you find exactly the same answer as SA would ask you.

    My approach isn't so different at all. but I mainly go through these steps.
    1. My first step is looking for the words that could be equated. For instance can I equate prudence= judging things only after weighing in different options? Cuz most of the time the stimulus try to confuse me with discrepancy in describing the same term.
    2. Look for the gap, as all people should
    3. Select candidate answer choices. There should be at least two or three answer choices that would be obviously irrelevant in establishing the conclusion or bridging the premises.
    4. Within the left choices, I do negation test.

    Negation test, I think is the best way to confirm an answer although it is time consuming. So I have to be very careful in selecting the candidate choices.

    The fundamental is this.
    If conclusion is true-> the assumption must be true.
    If assumption is not true-> Conclusion must be false.

    If an answer choice is a "necessary assumption," then when the choice is negated, it should destroy the conclusion.

    Suppose it is an Necessary Assumption question.

    Premise: All marines are rich. (M->R)
    Conclusion: All marines are devil fruit eaters. (M->DFE)

    If it was SA question the answer choice should say something like all rich people eat devil's fruits.(R->DFE) Then the connection is established. So this is a sufficient assumption.

    But this is definitely not a necessary assumption.

    Suppose some rich people don't eat devil's fruits.( negate the condition: all rich people eat devil's fruit) Does it falsify the conclusion? Not really.
    All marines may be awesome fighters and awesome fighters always eat devil's fruits. (M-> GF-> DFE)
    The very fact [rich-> devil fruit eaters] is not the only connection to make the conclusion valid means this is not a necessary assumption.

    But consider this condition " At least some rich people can eat devil's fruit"
    Negate it.
    And I get " Every single rich person cannot eat devil's fruit."
    If this is true, the conclusion is made invalid. I would say most of the NA answers do not contain definite language such as A is B or All As are B although sometimes they actually do. But it is definitely a good reason to doubt on the answer choice.

    May be I went on too long and probably you know this. I kinda wrapped up my thinking while writing this so anyway. In short, my strategy for NA is to identify the candidates and go though negation test.

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