Q5 - The museum's night security guard

[b91302310]

I'm quite confused about the answser. I know that there is a common structure between the stimulus and (B).(if one phenomena could not be explained by two evidences, there should be the third evidence in existence.)

However, I think that the argument of (B) is valid since if the price does not make profit or break even, it should be the one less than its cost. So, I think (B) is different from the stimulus in the validity.

Could anyone help to clear it up?

Thanks.

[ManhattanPrepLSAT1]

This one is tough being question number 5. Many people in my classes of the past have really struggled with this question. The reason why they typically have trouble with this one is that they never bothered to identify the flaw. Instead they just took the organization of the argument and tried to match its structure.

The flaw in the stimulus is that we cannot assume the night security guard is telling the truth. In fact, we have reason to suspect whether the night security is telling the truth. The reason is that the night museum guard has reason to hide the truth. If it were found out that the thief entered at the ground level, then there would be some fault on behalf of the guard.

So this argument appeals to an inappropriate authority. Answer choice (B) does the same thing. We have reason to suspect the claim made by the store's competitors.

So you're correct about the rest of the argument being valid, but we missed the flaw committed in the stimulus that we we're trying to match.

Does that help clear this one up?

[hdw217]

Hi there,
thanks for the explanation. but i'm confused. if the night security guard has reason to lie, aren't we questioning a premise?

at first i thought the flaw was the assumption that there 3 possible avenues to enter, up, ground, or below. Maybe they used teleportation or a portal? thats what got me to B, which was assumption that only "profit, broke even was possible".

[timmydoeslsat]

We are not questioning a premise. We certainly accept that this is what the security guard said. That is part is a fact. Whether or not what is says happened is a fact is up for grabs.

[b16]

I thought one of the basic rules of the LSAT was that the authors never lie and all premises are treated as fact (the truth). The point of logical reasoning is to evaluate the validity of the argument--there is never any evaluation beyond that, such as ulterior motives or deceit. Was that not the case in older LSATs?

[austindyoung]

I thought one of the basic rules of the LSAT was that the authors never lie and all premises are treated as fact (the truth). The point of logical reasoning is to evaluate the validity of the argument--there is never any evaluation beyond that, such as ulterior motives or deceit. Was that not the case in older LSATs?

Good question. I chose (B) for the same reason as another poster- which now that I see it may not be correct in this situation, but luckily it worked.

Let's turn this question into a Necessary Assumption question. The author says "therefore" the thieves MUST have gained access from below. A pretty reasonable deduction when they neither did it at or above the first floor.

Limiting ourselves to the current physical world we live in, I believe (if this were a Flaw Q) that a questionable answer choice would be "The argument assumes that because one option is the only imaginable option it is therefore the only option." Of course, it would be worded better, but it would pretty much be a False Dilemma flaw I think. But the problem here is that is is reasonable to argue that they did indeed come from below (yes, I'm ruling out instant transmission )

Once again to it being a Necc Assump Q- what's the assumption? Why is the argument assuming in order to be able to say "therefore"?

It's assuming the guard told the truth. If so, this argument is pretty airtight. If not, well....

And for Weaken Qs sometimes the correct AC weakens a premise.

HTH

[agersh144]

I thought one of the basic rules of the LSAT was that the authors never lie and all premises are treated as fact (the truth). The point of logical reasoning is to evaluate the validity of the argument--there is never any evaluation beyond that, such as ulterior motives or deceit. Was that not the case in older LSATs?

Can someone address this in greater detail...would a problem like this show up on a modern LSAT? If come October I need to question the integrity/motivation of the stimulus' character/protagonist that would be one extra layer that I want to know for sure and be cognizant of ahead of time!

[Mab6q]

Is there any other flaw besides the night security guard's statement. Without that, would the argument be valid. In other words, is the argument that because no one came in from at or above ground level, they must have came from below valid?

[tangdanni422]

I think Matt is right. LSAC wants us to see the difference between what was said and what happened.

Just for fun:

In the year of 2100, this question might be flawed for another problem, the stimulus assumes the thief has to enter the museum to stole the portrait. But for the 2100 technologies, this might not be necessary any more. So the thief does not have to enter the museum at any point at or above or below the ground level to stole the portrait (amazing!).

For the answer choice B, the passage assumes the store has paid some kind of cost for those shirts and thus concludes the customers has been able to buy the shirts at a price below the store's cost. Maybe the store was just selling those shirts on another store's behalf or got those shirts without any payment and therefore cost nothing. Or for the 2100 technologies, the store somehow did not incur a cost for those shirts (amazing!).

[christine.defenbaugh]

There are some fantastic questions raised in this thread! I want to clear this up once and for all: this is an absolutely CRITICAL concept for understanding arguments. It can (and does) appear on modern LSATs.

Everyone is correct that we are not allowed to question the truth of the premise itself. That does NOT mean that we are not allowed to question anything.

Imagine that your mother is a saint who never lies. Also imagine she has a terrible sister Betty who lies all the time. Unfortunately, your Mom is pretty gullible.

One day, she calls you in a panic, and says that Betty told her that bananas cause cancer. Now, you believe your mother, because your mother never lies. But what, exactly, do you believe your mother about? Do you accept that bananas cause cancer? Of course not!

What you accept is that Betty SAID these things. That's the part that you don't question. However, the truth of what Betty said is up for debate.

Similarly, if a premise was "The local news reported an explosion downtown". What you have to accept is the fact that the local news reported such a thing. You DO NOT have to accept that an explosion actually occurred. Look carefully at the different between these two premises.

Jane: I bought a dog.

Here, we have to believe Jane. We have to accept that she bought a dog.

Bob: Jane said she bought a dog.

Here, we have to believe Bob. So we have to believe the fact that Jane said it. But we DON'T have to believe [Jane. Thus, we don't have to believe that she did actually buy a dog.

Don't worry about the motivations for why someone might lie - just recognize that if the premise reports on what someone ELSE said, then we only have to accept the fact that they said it, not necessarily the truth of what that third party said.

Does that help clear this up a bit?

[WaltGrace1983]

Thanks, Christine ^

One question though: is there not still a false dilemma happening here? I totally get what you are saying with the appeal to an authority being the primary flaw here. Yet I cannot help but believe there are definitely still two flaws going on here. Under time, I had it between (A) and (B) and chose (B) because it both had the same structure using a potentially subjective source (the store's competitors) while (A) had a different flaw altogether. However, the main structure that I saw with B - one of the reasons that led me to pick it - was that false dilemma structure. What do you think?

(A) is a different flaw I call the Piece ≠ Puzzle (also Puzzle ≠ Piece). Just because the eventual winner was not the best in the two parts individually (the two pieces) does NOT mean that the winner was not the best in the whole in which those two parts consist. Here is another example...


I am a manager of a major league baseball team. My leadoff hitter will be the person who is the best, judging from total average and number of stolen bases. I am choosing between two guys: Babe Ruth and Willie Mays. Babe Ruth's average is .340 while Willie Mays's is .333. Babe Ruth has stolen only 1 base while Willie Mays has stolen 54. Who do I want as my leadoff hitter?

I clearly want Willie Mays. While, sure, Willie has a slightly lower overall batting average (.333 vs. 340), he is still the better overall leadoff hitter (from the criteria I selected). In other words, Willie might not be the best in each individual part, but certainly the best in the whole I have selected.


(C) This is a percentage ≠ number fallacy, completely different from what we are trying to find. In addition, there is a bit of a Puzzle ≠ Piece going on here because we are basing a conclusion on the population of all men on a premise talking only about married men.

(D) This is a scope flaw. Just because it is safe for two things, doesn't mean it is safe for two - only vaguely related - things.

(E) Who's to say that a plan was established? Maybe they simply won't accept the late questionnaires?

(B) truly comes the closest and deals with the same structure and flaw(s). It appeals to an inappropriate authority (the store's competitors) much like the original argument (security guard) while also perhaps making a false dilemma argument.

[christine.defenbaugh]

Interesting thoughts, WaltGrace1983!

While the stimulus does present only three options, I'm not sure that I'd actually characterize this as a false dilemma. A false dilemma inappropriate assumes that there are only a few options when in fact more exist. It is NOT a false dilemma when the two options presented are in fact the only options: you are either a penguin, or you are a non-penguin - no other options exist. So, a surefire false dilemma would be something like this:

The thieves could not have entered at ground level. Therefore they must have entered below ground level.

This argument ignores the possibility that the thieves could have entered above ground level.

But the original argument, if the security guard is reporting reality, seems more or less okay. If the thieves did not enter AT or ABOVE ground level, then they must have entered BELOW. What alternatives are being ignored here? (I suppose you could make an argument for direct teleportation, but that's really pushing it.)

Similarly, the argument in (B), assuming the competitors are reporting reality, seems pretty okay: either the store made a profit, broke even, or took a loss. There's no other real possibility. So if they didn't do the first two, then it's reasonable to conclude they did take a loss. The writers are a little more careless with the language here, but the idea that "the store's customers must have been able to buy shirts there at less than the store's cost" is simply conveying 'the store took a loss on the shirts'.

Now, regardless of whether this is a flaw or not, it's certainly a parallel structure between the stimulus and the answer choice, and I don't think that's a coincidence. But however parallel it is, it's not actually flawed logic.

I like your Puzzle =/= Piece description of (A)! Great breakdown there!

(C) This is a percentage ≠ number fallacy, completely different from what we are trying to find. In addition, there is a bit of a Puzzle ≠ Piece going on here because we are basing a conclusion on the population of all men on a premise talking only about married men.

This is an interesting answer choice, and I think actually has to be assessed with the knowledge that this PrepTest was administered in 1992, about 6 months before the Hawaii Supreme Court got everyone a flutter about the possibility of legal gay marriage in 1993. Given, that, it's likely that the answer choice was written with the implicit understanding that the percentage of married women and the percentage of married men were inherently tied together in a real numbers sense.

In light of that, this answer choice isn't nearly as flawed as you might think. If each married man is married to exactly one married woman, then the relative percentages actually might tell us something about the relative real numbers of these two groups. If this argument is flawed, it's flawed because it doesn't account for the possibility that some married people counted in the census are married to people NOT counted in the census (i.e., if half the married men's wives are in another country, then the the implication for the real numbers goes out the window).

In modern times, of course, this argument is deeply flawed because of the possibility of some significant number of the men being married to each other (and the same for the women).

At any rate, the point is that you shouldn't necessarily try to force every incorrect answer choice on a Parallel Flaw question into a Flaw box - the answer choice might not be flawed at all!

[WaltGrace1983]

Gotcha! I see what you are saying with the false dilemma stuff and that makes a lot of sense. Thanks a lot for the explanation.

[JeremyK460]

(C) This is a percentage ≠ number fallacy, completely different from what we are trying to find. In addition, there is a bit of a Puzzle ≠ Piece going on here because we are basing a conclusion on the population of all men on a premise talking only about married men.

This is an interesting answer choice, and I think actually has to be assessed with the knowledge that this PrepTest was administered in 1992, about 6 months before the Hawaii Supreme Court got everyone a flutter about the possibility of legal gay marriage in 1993. Given, that, it's likely that the answer choice was written with the implicit understanding that the percentage of married women and the percentage of married men were inherently tied together in a real numbers sense.

In light of that, this answer choice isn't nearly as flawed as you might think. If each married man is married to exactly one married woman, then the relative percentages actually might tell us something about the relative real numbers of these two groups. If this argument is flawed, it's flawed because it doesn't account for the possibility that some married people counted in the census are married to people NOT counted in the census (i.e., if half the married men's wives are in another country, then the the implication for the real numbers goes out the window).

In modern times, of course, this argument is deeply flawed because of the possibility of some significant number of the men being married to each other (and the same for the women).

At any rate, the point is that you shouldn't necessarily try to force every incorrect answer choice on a Parallel Flaw question into a Flaw box - the answer choice might not be flawed at all!

HEY! i recently filled out the census and it's very easy to say you're married when you're actually not. and a quick google search shows how often people actually BS the census. so, believing the census true or not, every census comes across issues of people lying specifically about marriage.