June 2007 LSAT Question Explanations June 2007 - Sec 2 - LR...

June 2007 - Sec 2 - LR - Q2

Video Transcript:

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Question two: All Labrador retrievers bark a great deal. All St. Bernard's bark
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infrequently. Each of Rose's dogs is a cross between a Labrador Retriever and a
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St. Bernard. Therefore, Rose's dogs are moderate barkers.
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Alright so argument or facts and clearly we have an argument. Therefore structural indicator. Our
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conclusion here is that Rose's dogs are moderate barkers. And how do we know that?
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Well, our first premise is that all Labrador Retrievers bark a great deal and then
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all St. Bernards bark infrequently. Rose's dogs are cross between these two types of
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dogs therefore they must have moderate barking.
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Just to break down this passage we know that 'all' is sufficient and necessary
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terminology that introduces a sufficient condition. So our our sufficient condition would be 'Labrador
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Retriever' and our necessary condition would be the other part of statement 'bark
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a great deal'. You notice the next sentence we also have 'all'. So again 'all' introduces sufficient so St.
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Bernard would be my sufficient condition. My necessary condition would be bark
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infrequently. So basically we have this spectrum of barking and we have Labrador
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Retrievers on one side and St. Bernard's on the other.
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This is infrequently whereas Labrador Retrievers
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bark a great deal. It tells us that Rose's dogs are a cross between these two
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types of dogs, Labrador Retrievers and St. Bernards, to conclude that Rose's dogs
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are moderate barkers. Clearly a flawed argument. How can we say that just
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because Labrador Retrievers bark a great deal St Bernards Berndards bark infrequently
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Rose's dogs are a cross. Therefore they must be moderate barkers. Doesn't make any sense
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but now that we have a clear understanding of this argument and we've
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identified that it is a flawed argument we turn our attention to the question stem.
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Which one of the following uses flawed reasoning that most closely resembles
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the flawed reasoning used in the argument above. So, you notice they point out for us that this is
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a flawed argument just in case you didn't notice. Again this is a flawed
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parallel resoning question. So now were going to look for an answer choice that has this exact same
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flaw, basically taking two sufficient and necessary conditions where you have Labrador
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Retriever sufficient for barking a great deal, St. Bernards sufficient for barking
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infrequently. Then have a combination of these two sufficient conditions to conclude that
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for some reason we're in the middle of the necessary conditions. Let's take a
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look at (A). All students who study diligently make good grades but some
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students who do not study diligently also make good grades. Jane studies
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somewhat diligently therefore Jane makes somewhat good grades. You noticed that (A) while
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flawed is not the same flaw that we saw in the passage so (A) would be eliminated.
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You notice 'all' again introduces sufficient so if you study diligently you make good grades
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and then tells us that Jane studies somewhat diligently so therefore she
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makes somewhat good grades. So that clearly makes no sense just because you have somewhat
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of the sufficient condition it doesn't mean you have somewhat of the necessary
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condition but that is not the problem that we saw in our passage so (A) would
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be eliminated. Moving to (B): All types A chemicals are extremely toxic to human
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beings all type B chemicals are non-toxic to human beings this household
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cleaner is a mixture of a type A chemical and a type B chemical therefore
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this household cleaner is moderately toxic.
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You notice just based on structure (B) seems like it's dead on but let's make
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sure. Again we know 'all' introduces sufficient so if you are type (A) you are extremely toxic.
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If you are type (B) you are not toxic. So again we have this spectrum. We have type (A) we have
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to (B). Again extremely toxic while (B) is non-toxic. It theb tells us that this household cleaner is a mixture
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of type A and type B to conclude that it is moderately toxic. And you
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notice that is the exact same flaw in the passage. We took two sufficient
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and necessary statements and then because something was a mix of the
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sufficient conditions we concluded that we have the middle of the necessary conditions.
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Right? Moderate Barkers. And in (B) we took the fact that A is extremely toxic B is
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non-toxic this household cleaner is a mixture of A and B
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therefore it is moderately toxic. Exact same flaw so (B) would be the correct
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answer. But again just making sure (C): All students and Hanson school live in
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Green County. All students at Edwards school live in Winn County. Members of the
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Perry family attend both Hansen and Edwards. Therefore, some members of the
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Perry family live in Greene County and some live in Winn County. Again (C)
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is a valid argument so it clearly cannot work. We are looking for
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flawed argument so (C) is out. Again you notice that 'all' again intoduces
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sufficient.
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So if you go to Hanson school that is sufficient for living in Greene County. If you go to
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Edwards school
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then you live in Winn County. Some members right of the Perry family attend
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both Hanson and Edwards. So we have people at Hanson school. We have people
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at Edwards School. And it takes that to conclude therefore we have some members
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of the Perry family living in Greene County and some living in Winn County. It's a valid argument.
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So (C) again would be eliminated just based on that we're looking for a flawed
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argument. Moving to (D): All transcriptionists know shorthand. All
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engineers know calculus. Bob has worked as both a transcriptionist and as an engineer.
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Therefore Bob knows both shorthand and calculus. Again (D) is a valid argument. So how
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could (D) be the correct answer? Again if you are a transcriptionist you know
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shorthand. If you are an engineer you know calculus. Bob has worked both as a
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transcriptionist and an engineer and take that to conclude that he knows
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shorthand and he knows calculus. Again, valid argument
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invoking sufficient to conclude necessary. But again not what we're looking for here.
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We're looking for a flawed argument which brings us to (E): All of Kenisha's dresses
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are very well made. All of Connie's dresses are very badly made. Half of the
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dresses in this closet are very well made, and half of them are very badly made.
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Therefore, half of the dresses in this closet are Kenisha's and half of them
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are Connie's. Clearly a flawed argument. But is it the same flaw? You notice that it is
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not. The problem here is that were saying if you were made by Keisha, Keisha's dresses are very
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well made. It then tells us that all of Connie's dresses are very poorly made or very badly made.
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Half of the dresses in this closet are very well made and half of them are
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very badly made. It then takes that to conclude that half of them are Kenisha's
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and half of them are Connie's but again the existence of the necessary condition
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tells us nothing about whether sufficient is present or not. Again just because
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I am a vegetable it doesn't necessarily mean I'm a carrot. We know all carrots are vegetables but you
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cannot say because something is a vegetable it is also a carrot. That is
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what's happening in (E). Don't just reverse but
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you notice again not the flaw we saw in the passage so (E) is eliminated.