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Author Topic: Need help with this flawed parallel reasoning question  (Read 1182 times)

crapola

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Need help with this flawed parallel reasoning question
« on: April 02, 2008, 01:58:14 AM »
Will someone please explain this question to me. I don't know the correct answer but I'm thinking it has to do with the word "maintains" in the stimulus. I also don't know why I'm baffled by this stupid question.

FYI. My diagnostic was a 134 so I know most of the members will find this question and future questions I post to be very easy. I just ask that you guys bear with me and understand where I'm coming from. I'm planning on taking the test in December.


The museum's night security guard maintains that the
thieves who stole the portrait did not enter the museum at
any point at or above ground level. Therefore, the thieves
must have gained access to the museum from below
ground level.

The flawed pattern of reasoning in the argument above is
most similar to that in which one of the following?

A. The rules stipulate the participants in the contest be
judged on both form and accuracy. The eventual winner
was judged highest in neither category, so there must be a
third criterion  that judges were free to invoke.

B. The store's competitors claim that the store in selling o
off the shirts at those prices, neither made any profit nor
broke even. Consequently, the store's customers must
have been able to buy shirts there at less than the store's
cost.

C. If the census is to be believed, the percentage of men
who are married is higher than the percentage of women
who are married. Thus, the census must show a higher
number of men than of women overall.

D. The product label establishes that this insecticide is
safe for both humans and pet. Therefore, the insecticide
must also be safe for such wild mammals as dear and
rabbits.

E. As had generally been expected, not all questionnaires
were sent in by the official deadline. It follows that plans
must have been made for the processing of questionnaires
received late.

mentor

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Re: Need help with this flawed parallel reasoning question
« Reply #1 on: April 02, 2008, 02:53:02 AM »
First off, this is a parallel flaw question.  That tells us to look for two things:

-a specific logical fallacy in the stimulus;
-the same structure and fallacy in one of the five answer choices.

Directing our attention to the stimulus:

The museum's night security guard maintains that the
thieves who stole the portrait did not enter the museum at
any point at or above ground level. Therefore, the thieves
must have gained access to the museum from below
ground level.

If we took the entire argument as if it came from the museum night guard, it seems to make sense; he says the thieves didn't enter at or above ground level, so they must have entered below ground level.  The problem is that it is not the museum guard making the argument in question.  An unnamed author poses the argument based on what the security guard says:

P: Night guard says thieves didn't enter at ground level or above
C: They therefore entered below ground level.

See the problem?  We conclude that a specific event happens based on what somebody claims without establishing the veracity of the claim.  We don't know if the security guard is correct in what he maintains - maybe he was sleeping or off taking a dump during the break-in.

Now look at answer choice B:

B. The store's competitors claim that the store in selling
off the shirts at those prices, neither made any profit nor
broke even. Consequently, the store's customers must
have been able to buy shirts there at less than the store's
cost.

Do we have a conclusion based on evidence present only in a related party's claim without verification?  We sure do - the store's competitors are offering us information about the store's lack of profitability.  We don't know if it's true, yet we reach a conclusion about the store's pricing as if it were written in stone.
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ssilver0210

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Re: Need help with this flawed parallel reasoning question
« Reply #2 on: April 02, 2008, 07:02:34 PM »
Be sure to first pick out the flawed pattern of reasoning in the stimulus.

Flaw: A statement must be true (the thieves gained access below ground level), because someone (the guard) says it's true. There is no evidence to back up why the statement must be true, and presenting a conclusion without providing a basis for that conclusion is flawed reasoning.

The key word here is must.  A word like "must", although it might not seem all that significant, truly make the difference is these kinds of questions. Other choices might be very similar, but the correct answer choice could be determined based on one word. So read really carefully, and develop the skill of reading each word independently while also understanding the context of the entire passage ( a skill which doesn't necessarily come naturally, and isn't necessarily taught throughout school. Doing so will help you to improve on the LSAT.

Once you've found the flaw, match it up with the same flaw in one of the answer choices.

In choice B, a statement must be true (customers buy shirts at less than store's cost) because someone (store's competitor) says it's true. A conclusion is presented without an adequate basis for stating that conclusion.

It's a perfect match, and the answer choice presents a parallel flaw to the flaw in the stimulus.
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crapola

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Thank you!
« Reply #3 on: April 10, 2008, 02:42:35 AM »
I just wanted to thank you both for the explanations. I have not been online much but I have been studying constantly and I do believe I am getting better and faster at it.

This forum is great. :)

ssilver0210

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Re: Need help with this flawed parallel reasoning question
« Reply #4 on: April 10, 2008, 11:35:56 PM »
Happy to help.
I provide tutoring both for the LSAT and the MBE at very reasonable rates.  I provide a free hour to all students to try out the tutoring.  Feel free to contact me at silvermanbarprep@gmail.com for tutoring inquires or to set up a free lesson. Visit my blog @ http://www.mbetutorial.blogspot.com