Help with LR question

kaitlyn00
Posts: 10
Joined: Mon Jul 08, 2013 11:32 pm

Help with LR question

Postby kaitlyn00 » Mon Jul 08, 2013 11:34 pm

Can anyone help me understand this question?

No one who works at Layla's Electronics has received both a poor performance evaluation and a raise. Lester has not received a raise, so it must be that he has received a poor performance evaluation.

The flawed reasoning in the argument above is most similar to the reasoning in which of the following arguments?

A. No one who lives in a house both owns it and pays rent on it. So, since my next-door neighbors pay rent on their house, it must be that they do not own it.
B. No one who lives in a house both owns it and pays rent on it. My next-door neighbors own their house. Therefore it must be that they do not pay rent on it.
C. My neighbors have not paid any rent on their house. Since anyone who lives in a house but does not rent it owns it, it must be that they own it.
D. My next-door neighbors do not own their house. Since no one who lives in a house both owns it and pays rent on it, it must be at my next-door neighbors pay rent on their house.
E. Anyone who lives in a house but does not own it pays rent on it. My next-door neighbors do not own their house. Therefore it must be that they pay rent on it.

The credited response is D.

magickware
Posts: 359
Joined: Sun Nov 04, 2012 1:27 pm

Re: Help with LR question

Postby magickware » Mon Jul 08, 2013 11:45 pm

The flaw there is that the stimulus creates a false connection between the poor performance evaluation and the raise. Just because Lester didn't receive a raise doesn't mean that he must have received a poor performance evaluation. Maybe people might not get either of them.

A-No flaw.
B-No flaw.
C-No flaw.
D-Exact same kind of flaw as the stimulus, and the wording matches as well. Look for it.
E-No flaw.

kaitlyn00
Posts: 10
Joined: Mon Jul 08, 2013 11:32 pm

Re: Help with LR question

Postby kaitlyn00 » Mon Jul 08, 2013 11:57 pm

magickware wrote:The flaw there is that the stimulus creates a false connection between the poor performance evaluation and the raise. Just because Lester didn't receive a raise doesn't mean that he must have received a poor performance evaluation. Maybe people might not get either of them.

A-No flaw.
B-No flaw.
C-No flaw.
D-Exact same kind of flaw as the stimulus, and the wording matches as well. Look for it.
E-No flaw.



I understand the flaw in the stimulus. I do not understand why D is the correct answer. I would appreciate a more detailed explanation if anyone has the opportunity to provide it.

Cambridge LSAT
Posts: 270
Joined: Mon Aug 24, 2009 3:26 pm

Re: Help with LR question

Postby Cambridge LSAT » Tue Jul 09, 2013 12:03 am

Here's the stimulus diagrammed:
poor performance evaluation → ~raise (premise)
raise → ~poor performance evaluation (contrapositive)
~raise → poor performance evaluation (conclusion)

The speaker concludes against the arrow, which is a faulty inference.

Now, let's look at D:
owns house → ~pay rent (premise)
pays rent → ~own house (contrapositive)
~own house → pays rent (conclusion)

Choice D makes the same faulty inference by simply reversing the terms (without negating them) and concluding against the arrow.

As magickware mentioned, this is a common flaw. Here's another example of this flaw in action:
"A shape can't be both a circle and a square. Since this shape isn't a square, it must be a circle."

magickware
Posts: 359
Joined: Sun Nov 04, 2012 1:27 pm

Re: Help with LR question

Postby magickware » Tue Jul 09, 2013 12:04 am

The stimulus-
No one who works at Layla's Electronics has received both a poor performance evaluation and a raise. Lester has not received a raise, so it must be that he has received a poor performance evaluation.

D arranged and edited to match the stimulus.

No one who lives in a house both owns it and pays rent on it. My next-door neighbors do not own their house, so it must be that my next-door neighbors pay rent on their house.

One common "trick" that LSAC will use on parallel flaw questions is to rearrange the sentence to mix people up. That's why it's a lot easier to just follow the flaw than the sentence structure.

magickware
Posts: 359
Joined: Sun Nov 04, 2012 1:27 pm

Re: Help with LR question

Postby magickware » Tue Jul 09, 2013 12:08 am

Cambridge LSAT wrote:Here's the stimulus diagrammed:
poor performance evaluation → ~raise (premise)
raise → ~poor performance evaluation (contrapositive)
~raise → poor performance evaluation (conclusion)

The speaker concludes against the arrow, which is a faulty inference.


I was thinking on this line, but I was tripped up by the wording. Now I realize that I had a brain-fart. Somehow I forgot that

poor performance evaluation->-raise

and

raise->-poor performance evaluation

were contrapositives of one another.

=( Need to study more.

kaitlyn00
Posts: 10
Joined: Mon Jul 08, 2013 11:32 pm

Re: Help with LR question

Postby kaitlyn00 » Tue Jul 09, 2013 12:27 am

Cambridge LSAT wrote:Here's the stimulus diagrammed:
poor performance evaluation → ~raise (premise)
raise → ~poor performance evaluation (contrapositive)
~raise → poor performance evaluation (conclusion)

The speaker concludes against the arrow, which is a faulty inference.

Now, let's look at D:
owns house → ~pay rent (premise)
pays rent → ~own house (contrapositive)
~own house → pays rent (conclusion)

Choice D makes the same faulty inference by simply reversing the terms (without negating them) and concluding against the arrow.

As magickware mentioned, this is a common flaw. Here's another example of this flaw in action:
"A shape can't be both a circle and a square. Since this shape isn't a square, it must be a circle."


Thank you! I completely understand now.




Return to “LSAT Prep and Discussion Forum”

Who is online

Users browsing this forum: 34iplaw, DumbHollywoodActor, Thomas Hagan, ESQ., VMars, Vursz and 12 guests