PT17.S2.Q21 - nuclear reactors are sometimes built

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• 1 Like

  jknauf Alum Member

  May 2017 edited May 2017 1741 karma

  So as a premise, we are given the idea that at MAX there is 1 earthquake every 100,000 years. Answer choice E, is saying at minimum there is 1 earthquake every 100,000 years. So if I negate that, or say there is at minimum 0 earthquakes per 100,000 years, how does that effect our argument?

  Does our argument still stand without it? Can our conclusion: Out of all the potential nuclear reactor sites in such a region, the ones that are least likely to be struck by an earthquake are ones located near a fault that has produced an earthquake within living memory still be true? Is it absolutely necessary that we have at minimum 1 earthquake per 100,000 years?
• GrecoRoman Alum Member

  May 2017 140 karma

  You make a really good point. Nothing states that minor faults have to produce earthquakes so the minor faults least likely to be hit by one would be the ones that don't produce earthquakes because they would always have a 0% chance rather than the ones that will produce another in 99,000+ years. I guess the only way to make E not necessary would be to assume that minor faults that have recently had earthquakes are also at 0% chance of earthquakes for the next 99,000+ years and that the nuclear power plant is only concerned about it's chances of earthquakes happening in the relatively near future. That way the faults that never produce earthquakes and the faults that have recently produced earthquakes are both equal at 0% chance for the relevant period of the nuclear power plants lifetime and then the conclusion can still be true even if there are minor faults that produce no earthquakes. The older LSATs aren't as clear cut as the newer ones so I wouldn't worry about missing that. Great job at noticing that.
• Sarah889 Alum Member

  May 2017 877 karma

  @jknauf Well, if we negate the premise (at least how I am understanding it) that there are some faults/regions that have NO earthquakes, then, yes, it will render the conclusion highly suspect. (I see now that C is necessary to make the negation of E render the conclusion invalid; E doesn't get us all the way there, but it does get is to a point of high suspicion). The conclusion is saying that the nuclear reactors least likely to be struck with an earthquake are the ones that are near faults that have recently had an earthquake. If there are some faults that never have earthquakes, than our conclusion would not be the case. In fact, the nuclear reactors least likely to be struck with an earthquake are the ones near the faults that never have earthquakes. I do see what you're saying though and I think I understand now why C is more correct, as described to @"work all week" below.

  @"work all week" Thanks for your response. I think the reason why C is "more correct" is because it might be "more necessary," if that makes sense. For example, even if we establish that all the faults are active, we would still need to establish the proximity assumption. If none of the nuclear reactors where near any faults, then I guess it would not make a difference if the faults were active or not. This might be one of those cases where we have to assess which answer is "more necessary." I believe E would be an appropriate answer if the stimulus already established the relative placement assumption.
• DumbHollywoodActor Alum Inactive ⭐

  May 2017 edited May 2017 7468 karma

  I'm not certain that necessity can be qualified. In other words, one necessary assumption is not more necessary than another. Admittedly, this is a very tricky stimulus that's both modifier- and referential-phrase-crazy, but I need to ask you a question: How would you negate answer E?

  It hard to surmise because I haven't seen your negation, but I think your negation would be something like this: "Earthquake faults in geologically quiet regions can never produce earthquakes." I realize I'm oversimplifying and I'm not trying to "straw man" you. I'm merely writing it this way because it would clearly be a necessary assumption. Unfortunately, that is not what the negation of answer choice E is doing.

  My version is that "earthquake faults in geologically quiet regions, if they produce earthquakes, do so after 100,000 years have gone by."

  Before I address why this negation doesn't destroy the argument and, thus, why the answer isn't necessary, I think I need to address this question's difficulty, which is in the wording. I'll attempt to clarify what the argument is saying, thereby making it clear (hopefully) why C is the correct answer and E is an incorrect answer.

  The argument's conclusion is making a comparison about the likelihood of being struck by an earthquake:

  (1)Nuclear reactor sites located near a fault that has had an earthquake within living memory in geologically quiet region

  vs.

  (2)All other nuclear reactor sites NOT located near a fault that has had an earthquake within living memory in a geologically quiet region.

  In this case, quite simply (1) beats (2) in terms of being less likely to get hit by a future earthquake. Why is it making this comparison? Because minor faults in geologically quiet regions NEVER produce an earthquake more often than once in any given 100,000- year period.

  Answer C is correct because it rules out the possibility that a (2) nuclear reactor, though still in a geologically quiet region, isn't hundreds of miles away from any faults. period. Because if it weren't near a fault, we can't conclude that (1) beats (2) in terms of being less likely to get hit by a future earthquake.

  Answer E, instead of addressing where the nuclear reactors are located like C does, addresses the time it would take for an earthquake to hit. In other words, it's not addressing the key distinction made in the conclusion: its location. The time it would take for an earthquake to hit addresses both (1) and (2) nuclear sites equally and would have no impact on the distinction that the conclusion is making.

  This is a very tricky question, but I hope this helps you see how E isn't necessary .
• jknauf Alum Member

  May 2017 edited May 2017 1741 karma

  Everything posted above by, @DumbHollywoodActor addressed your questions. A few side notes though.

  @bswise2 said:
  @jknauf
  but it does get us to a point of high suspicion.

  Maybe, but is our goal to weaken the argument?

  @bswise2 said:
  I think the reason why C is "more correct" is because it might be "more necessary," if that makes sense. For example, even if we establish that all the faults are active, we would still need to establish the proximity assumption. If none of the nuclear reactors where near any faults, then I guess it would not make a difference if the faults were active or not. This might be one of those cases where we have to assess which answer is "more necessary."

  For a necessary assumption question, the answers are either necessary or they aren't. There is no in between. If both assumptions were required by the argument, there would be two right answer choices.
• GrecoRoman Alum Member

  May 2017 edited May 2017 140 karma

  @DumbHollywoodActor That's some good input but if you think about it the stimulus allows for there to be minor faults that don't produce earthquakes at all. If that is the case, then we would have the same problem for the conclusion that we would if potential sites were allowed to be away from any minor fault lines. Both of those potential sites would be less likely to have an earthquake than a site near a minor fault that produces earthquakes.

  Thinking about this more I think that E is wrong because it's more of a sufficient assumption attempting to address the problem of minor faults that produce no earthquakes. Negating it would just be "Earthquake faults in geologically quiet regions do not produce earthquakes at least once every 100,000 years". That would be fine since we could have them happen at least once every 100,001 years to do nearly the same job. So I think the necessary assumption that we wanted E to be would have been "all minor faults in geologically quiet regions are capable of producing earthquakes".
• DumbHollywoodActor Alum Inactive ⭐

  May 2017 edited May 2017 7468 karma

  @"work all week" said:
  @DumbHollywoodActor That's some good input but if you think about it the stimulus allows for there to be minor faults that don't produce earthquakes at all. If that is the case, then we would have the same problem for the conclusion that we would if potential sites were allowed to be away from any minor fault lines. Both of those potential sites would be less likely to have an earthquake than a site near a minor fault that produces earthquakes.

  Thank you, but I'm not sure how "minor faults that don't produce earthquakes at all' is relevant to this particular question since no answer choices addresses those kinds of minor faults. I think if there was an answer that addressed this issue, you'd be on to something, but alas, it's not. In other words, there's more than one possible necessary assumption. We can only go for the answers they give us.

  Thinking about this more I think that E is wrong because it's more of a sufficient assumption attempting to address the problem of minor faults that produce no earthquakes.

  If it was a sufficient assumption, then it would mean that we have a valid argument. I'm not sure how you come by that reasoning. Which valid argument type would that even be?

  We have a comparative conclusion that makes distinctions about location of nuclear reactor sites, but we have no premises to support that distinction. For E to be a sufficient assumption, it would have to address that deficiency. I hope that you can see that it clearly doesn't. A sufficient assumption would be something like this:

  "If minor faults in a geologically quiet region never produces an earthquake more often than once in any given 100,000-year period, then any nuclear reactor near a fault line that has produced an earthquake within living memory in a geologically quiet region is less likely to be struck by an earthquake than one that is not near such a fault line."

  " So I think the necessary assumption that we wanted E to be would have been "all minor faults in geologically quiet regions are capable of producing earthquakes".">

  On this, I whole-heartedly agree! That's why I surmised that she might have thought that E negated said, "Earthquake faults in geologically quiet regions can never produce earthquakes." It's the negation of your necessary assumption that we wanted. My bad on not being clear there.
• GrecoRoman Alum Member

  May 2017 140 karma

  Good discussion. That is true it, E can't be a sufficient assumption without addressing all the gaps of the argument. It's a good trap answer that appears to address one problem but actually doesn't. Cheers.
• 1 Like

  DumbHollywoodActor Alum Inactive ⭐

  May 2017 7468 karma

  @"work all week" you're absolutely right about everything, answer choice E being a tantalizing trap answer---it just "feels" like a correct NA answer, while answer C with its "every" "feels" too strong to be an NA (That's why it's so important on NAs to have iron-clad understanding of the stimulus)---- and a good discussion ----- the purpose of this forum. I've spent many a keyboard click arguing this way or that about a particular answer choice, and each one contributed to my overall understanding of the test. Thanks and so happy to have you with us.
• Sarah889 Alum Member

  June 2017 edited June 2017 877 karma

  @"work all week" @DumbHollywoodActor Thank you both for this back and forth. Reading your interpretations really illuminates the different ways to approach this question.

  BTW, @DumbHollywoodActor I don't consider the negation of E to be that "Faults in geologically quiet regions NEVER produce earthquakes." I consider the negation to be that "Faults in geologically quiet regions do not always produce earthquakes every 100,000 years." This, in conjunction with the stimulus (maxing the amount of earthquakes at 1 every 100,000 years) leaves us with the possibility that there are some faults that do not produce any earthquakes.

  @DumbHollywoodActor said:

  Thank you, but I'm not sure how "minor faults that don't produce earthquakes at all' is relevant to this particular question since no answer choices addresses those kinds of minor faults. I think if there was an answer that addressed this issue, you'd be on to something, but alas, it's not. In other words, there's more than one possible necessary assumption. We can only go for the answers they give us.

  Just wanted to clarify this...it seemed as though it was not clear above regarding why these inactive faults were brought up. The reason is because I believe the negation of E provides for the possibility of these inactive faults, hence why I'm contesting the fact that it's not a necessary assumption.
• DumbHollywoodActor Alum Inactive ⭐

  June 2017 edited June 2017 7468 karma

  I > @bswise2 said:
  This, in conjunction with the stimulus (maxing the amount of earthquakes at 1 every 100,000 years) leaves us with the possibility that there are some faults that do not produce any earthquakes.

  The reason is because I believe the negation of E provides for the possibility of these inactive faults, hence why I'm contesting the fact that it's not a necessary assumption.

  I figured I was straw-man-ing your argument (forgive me for that. I only wished to find a re-wording for answer choice E that would, in my opinion, lead to a necessary assumption.) , but your explanation above now, I think, helps me see your reasoning error: your interpretation of necessity is more liberal than LSAC's definition. A negated necessary assumption can't merely leave open the possibility that the conclusion is false. It must definitively vanquish all possibilities that the conclusion is true.

  In other words, even if there is the possibility that there are some faults that do not produce any earthquakes, it's also still possible that all faults do eventually produce earthquakes, and, thus, it also still possible that (1)nuclear reactor sites located near a fault that has had an earthquake within living memory in geologically quiet region are less likely to be struck by an earthquake than (2) all other nuclear reactor sites NOT located near a fault that has had an earthquake within living memory in a geologically quiet region. True, your negated version makes the conclusion LESS likely than before, but not impossible. Hope this helps.