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#25812
Complete Question Explanation

Parallel Flaw—FL. The correct answer choice is (B)

Formal Logic is tested infrequently, but makes an appearance in this question, with the terms some, most, and all forming the basis of the relationships we need to understand to evaluate the conclusion. The conclusion appears in the second half of the first sentence, but despite its placement in the stimulus, we will address it last.

We are told that there has been a recent theft of three million dollars from the City Treasurer’s Office, and that the “suspects are all former employees of the City Treasurer’s Office.” We can diagram this statement as:

S = suspects
E-CTO = former employees of the City Treasurer’s Office
  • S ..... :arrow: ..... E-CTO
Next, we are told that the mayor’s staff includes (i.e., some are) former employees of the City Treasurer’s Office:

MS = mayor’s staff
  • MS ..... :some: ..... E-CTO
Because a relationship using the term some is reversible, we can connect these two relationships across the common term E-CTO:
  • S ..... :arrow: ..... E-CTO ..... :some: ..... MS
Our understanding of Formal Logic tells us that this diagram will not produce an inference. It may be the case that the group of former employees of the City Treasurer’s Office (E-CTO) is so large that even though all suspects (S) are a member of that group, and some members of the mayor’s staff (MS) are also members of that group, the groups E-CTO and MS do not overlap.

However, the author does not have our grasp of Formal Logic, and mistakenly comes to the conclusion that some members of the mayor’s staff are suspects:

MS = mayor’s staff
S = suspects
  • MS ..... :some: ..... S
Based on the analysis above, this conclusion is flawed. The question stem tells us that this is a Method of Reasoning—Flaw question. Our prephrase is that the correct answer choice will contain a flawed inference about some of a group derived by improperly chaining together a some relationship to an all relationship.

It is far too time-consuming to map out the Formal Logic relationships in each of the answer choices. Fortunately, you do not have to. Start by using the Double the Conclusion Test to compare the conclusions in each answer choice to the conclusion in the stimulus. To match, it must be a some relationship. Next, use the Premise Test to compare the premises. In order to match the argumentation in the stimulus, there must be two relationships, an all relationship and a some relationship. Any answer that fails to match in both ways will be incorrect. In this case, only answer choice (B) passes both the Double the Conclusion Test and the Premise Test.

Answer choice (A): This answer choice is incorrect, because its premises are both some relationships, rather than one some and one all relationship.

Answer choice (B): This is the correct answer choice, and may be diagrammed as:

S = skyscrapers
B = buildings
C = cabins
  • S ..... :arrow: ..... B ..... :some: ..... C, therefore: S ..... :some: ..... C
As with the flaw in the stimulus, it may be the case that the buildings group may be so large that the cabins and skyscrapers groups do not overlap.

Answer choice (C): This choice has two all premises, rather than an all premise and a some premise.

Answer choice (D): This answer choice has an all conclusion, rather than a some conclusion.

Answer choice (E): As with answer choice (D), this choice has an all conclusion.
 agroves
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#11490
Hello,

I eventually got this question correct by looking at the language of 'some' and 'all' and also drawing diagrams, but it took a lot of time. Any suggestions on a quick way to solve this question?

Thank you!

Angela
 Adam Tyson
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#11502
Like you, agroves, I found myself focusing on the language and taking some time with this parallel reasoning question. I started by doubling the conclusion - my stimulus concluded that some members of the mayor's staff are suspects, so I need a conclusion that follows that language of "some A are B." That quickly knocks out answers D and E, whose conclusions are "all A are B".

Next, I focused on doubling the premises - I have two of them in the stimulus: 1) All suspects are former employees of CTO, and 2) some of the staff are also former members of CTO. I want premises that say "All X are Y" and "some Z are also Y". That eliminates answer A (two "some" premises) and answer C (two "all" premises). That leaves only answer B, which matches my premises and my conclusion better than any of the others.

Where I got hung up was on over-analyzing answer B, and deciding I didn't like the way the direction of my formal logic arrows there weren't perfectly matching the ones in the stimulus. I had to remind myself that we aren't always looking for great answers, or even good ones - we're only looking for the best answer out of the five we are given, even if that best answer is a bit of a stinker.

Often we can approach parallel reasoning, conditional reasoning, justify and assumption questions, among others, with a very mechanical mindset. Don't worry about whether it makes sense or not, just follow the strategies you've learned with confidence and no second-guessing, and the right answers will usually follow.

Hope that helped!
 akshanye
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#72003
I’m trying to figure out how you got some from the premise “..the mayors staff includes former employees of that office.” Is include synonymous with some?
 Zach Foreman
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#72027
Akshanye,
Yes, they are synonymous. X includes Y. Some X are Y. How can we know this? We can try some groups that we know and see what happens. "Congress includes Democrats" "Some in Congress are Democrats". "Stars include our sun." "Some stars are our sun."
Another way to think about it is that "the staff includes former Treasury employees" can be rephrased as "some staff are former Treasury employees" or "at least one staff member is a former Treasury employee."
 bella243
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#78845
Adam Tyson wrote:Like you, agroves, I found myself focusing on the language and taking some time with this parallel reasoning question. I started by doubling the conclusion - my stimulus concluded that some members of the mayor's staff are suspects, so I need a conclusion that follows that language of "some A are B." That quickly knocks out answers D and E, whose conclusions are "all A are B".

Next, I focused on doubling the premises - I have two of them in the stimulus: 1) All suspects are former employees of CTO, and 2) some of the staff are also former members of CTO. I want premises that say "All X are Y" and "some Z are also Y". That eliminates answer A (two "some" premises) and answer C (two "all" premises). That leaves only answer B, which matches my premises and my conclusion better than any of the others.

Where I got hung up was on over-analyzing answer B, and deciding I didn't like the way the direction of my formal logic arrows there weren't perfectly matching the ones in the stimulus. I had to remind myself that we aren't always looking for great answers, or even good ones - we're only looking for the best answer out of the five we are given, even if that best answer is a bit of a stinker.

Often we can approach parallel reasoning, conditional reasoning, justify and assumption questions, among others, with a very mechanical mindset. Don't worry about whether it makes sense or not, just follow the strategies you've learned with confidence and no second-guessing, and the right answers will usually follow.

Hope that helped!


Hi Adam,

Could you please elaborate on the use of the mechanistic approach on justify and assumption questions? I understand how parallel and conditional questions can be mechanistic, and I do understand the theory behind the justify formula. But I still find assumption and especially justify questions more tricky when it comes to using a mechanistic approach. Justify questions in particular tend to make little common sense because of typically large gaps between the premises and the conclusion.
 VamosRafa19
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#81157
Hi,

I thought "all" was a sufficient condition indicator, so shouldn't the first part be E-CTO :arrow: S?

I got the right diagram from how the conclusion was worded, but I just assumed the author of the stimulus incorrectly said S :arrow: E-CTO.
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 KelseyWoods
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#81191
Hi all!

Bella: Justify and Assumption questions can often be thought of mechanistically precisely because of those large gaps between the premises and the conclusion. You're looking for an answer choice that fills in that gap, or creates a link between the premises and the conclusion. This typically means that if there is new information in the conclusion--info that was not in the premises--that new info also has to be in the correct answer. The correct answer should then link that new info back to the premises. Because of this mechanistic nature, you can often prephrase the answers to these questions very specifically. Check out this podcast episode for further discussion on the mechanistic approach to Justify questions:
https://blog.powerscore.com/lsat/lsat-p ... questions/


VamosRafa19: You are correct that "all" is a sufficient condition indicator term. But you have to be a little careful when using indicator terms. The sufficient condition is whichever condition "all" modifies. Typically, indicator words come before the terms they modify, but this is not always the case. Here, the statement says: "The suspects are all former employees of the City Treasurer’s Office." Based on that wording, is "all" referring to the suspects or to the former employees? Are all suspects former employees? Or are all former employees suspects? The "all" is referring to the suspects. "The suspects are all" means that the statement is giving you a characteristic of all of the suspects. Thus, the correct diagramming of that statement is S :arrow: E-CTO.

Hope this helps!

Best,
Kelsey

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