PT59.S3.Q13 - study of automobile accidents

CJ ShinCJ Shin Free Trial Member
edited December 2015 in Logical Reasoning 302 karma
Hey guys, first of all here is the link to this question.
http://7sage.com/lsat_explanations/lsat-59-section-3-question-13/

I seem to be having a lot of problem with questions that require mathematical understanding.
I got this question right through POE, but having a real hard time trying to understand why the correct answer is correct.

So the premise is about the relative difference in the percentage of INJURY between accidents involving large and small cars within the sample of 10,000 accidents (large cars = lower, small cars higher percentage).
And the conclusion is about the general likelihood of being INJURED in large vs. small car accidents (large cars safer).

So far so good, but.. where the hell is the FLAW?

Jon explains the shift in scope by saying that the conclusion is about ABSOLUTE numbers, and it would make sense if it is indeed about absolute numbers (remember, percentage -> absolute number is flawed).
BUT, the conclusion explicitly states "one is less LIKELY," which does not seem to indicate absolute numbers.

Please help!!

Comments

  • J.Y. PingJ.Y. Ping Administrator Instructor
    14205 karma
    You gotta be careful when they tell you that these 10,000 were already in accidents. At that point, it just doesn't matter. They're already in accidents.

    Look at the conclusion in isolation. How would you try to prove it? Large cars are safer than smaller cars. The two things that matter are the odds of getting into an accident and the severity of the injury. You take the odds and weight those odds by the severity.

    Our existing premises only talk about the severity of injury. Large cars in accidents had a lower average severity of injury than smaller cars in accidents.

    Okay, but what about the odds of getting into an accident in the first place?
  • CJ ShinCJ Shin Free Trial Member
    302 karma
    Hey JY, thanks for your input.

    When I was reviewing this question by myself without looking at the explanation, I actually paraphrased the conclusion exactly the same as yours: large cars are safer than smaller cars. Your explanation of jumping from "severity of injury" to "safety in general" makes a lot more sense. I guess the explanation confused me more because of the idea of ABSOLUTE numbers that did not seem to match stimulus.

    So would you say that the flaw is not about % -> #, but rather an "incomplete" premise?
  • J.Y. PingJ.Y. Ping Administrator Instructor
    14205 karma
    "about % and #" is very vague. It's kind of "about" those things since % and # are involved...
  • Angelica PicklesAngelica Pickles Alum Member
    28 karma
    Just thought I might share my thought process:

    I immediately noted that they're giving us a percentage (% injured) of a percentage (%large car/small car drivers) of the 10,000. We know nothing about the second%.

    For the sake of simplifying things, let's assume that only small cars or large cars (so no medium, x-small, etc cars) were driven and fill in some numbers:

    90% of small car injured
    10% of large car injured

    but 90% of what? 10% of what? of 10,000? That's what they're trying to get you to assume but no, 90% of small car, which itself is a % of 10,000.

    Depending on what we plug in for this unknown second percentage, we can either strengthen or weaken this conclusion.

    Let's say, as D) does, that %small car < %large car

    1% small car, so 90% of 1% of 10,000 = 90 injured
    99% large car, so 10% of 99% of 10,000 = 990 (!!!) injured

    Manipulated this way, ALL THE PREMISES HOLD, we're still saying %injured small car > % injured large car. But now it seems it would make more sense to conclude the opposite of what is concluded in the stim.
    I think this is what Jon was getting at when he was talking about absolute numbers.
    Usually when we're given %s, they're floating around, not really pinned down to anything, like in this problem. Obviously I didn't actually do the math for this problem; once I realized that the second % was not provided (=the assumption) I went straight to the acs to look for it.

    Let me know your thoughts!
  • CJ ShinCJ Shin Free Trial Member
    302 karma
    AH! That is a great way of explaining this question, % of %.
    That clears it up. Thank you very much!
  • Angelica PicklesAngelica Pickles Alum Member
    28 karma
    Sure thing!
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