#25 - Economist: No economic system that is centrally

[Administrator]

Complete Question Explanation

Parallel Reasoning—SN. The correct answer choice is (B)

This is a "Parallel Reasoning" question. The economist's argument goes as follows:

• 1. Centrally planned economy allocate efficiently
  
  (Note the contrapositive: allocate efficiently CP.)
  
  2. Debt<5% allocate efficiently
  
  (Note the contrapositive: allocate efficiently Debt<5%)
  
  3. Conclusion: Centrally planned economy Debt <5%.

This argument is valid. By stringing premise (1) together with the contrapositive of premise (2), we get the conclusion.

We need to find an answer choice with the same pattern of reasoning. Any answer choice with flawed reasoning is not the correct answer!

Answer choice (A): This is valid reasoning, but the logical chain rests on the relation of a subgroup to a main group (some mammals are bats) which is not the same logic as in the stimulus.

Answer choice (B): This is the correct answer choice.

• 1. Air pollution problems Large concentration of automobiles
  
  (Contrapositive: Large concentration of automobiles Air pollution problems)
  
  2. Rural districts Large concentration of automobiles
  
  (Contrapositive: Large concentration of automobiles Rural districts)
  
  3. Conclusion: Rural districts Air pollution problems

This is valid reasoning just like the stimulus. We get this conclusion by stringing together premise (2) plus the contrapositive of premise (1). This is the correct answer choice.

Answer choice (C): Note that the conclusion involves the qualified term "unlikely" rather than a definite statement, like the conclusion in the stimulus. This cannot be the correct answer choice.

Answer choice (D):

• 1. Famous rock star Own record company
  
  2. Famous rock star
  and Receive extra company profits
  Own Record Company
  
  The correct conclusion is: Famous rock star Receive extra company profits.

However, the conclusion stated is: Famous rock star Receive large regular royalties.
This is not the right conclusion.

This logic is flawed, so this is not the correct answer choice.

Answer choice (E): The first premise alone (every mutual fund managers knows an insider trader) is enough to establish the conclusion: There is no mutual fund manager who is unknown to every insider trader. (Assume that "know" is a bilateral relation, so if X knows Y, then Y knows X.) This logical form is not like the stimulus.

[Sherry001]

Hello ,
Could you kindly let me know if this is a flawed argument or not ?
I say this because I saw the stimulus as mistaken reversal /mistaken negation ( I mix these terms all the time ) but the question stem doesn't indicate that it is flawed . (Unless I have diagramed wrong ).

1- ECO---> cannot allocate resources
2- National debt -5% --> allocate resources

Cl: ECO--> National debt -5%

Thanks so much
Sherry

[Steve Stein]

Hey Sherry,

That's a good question; let's take a look at the argument piece by piece:

If an economy is centrally planned, it cannot allocate resources efficiently:

• Centrally planned economy allocate efficiently

Efficient allocation is necessary for a national debt under 5%, which means that if you cannot allocate efficiently, you cannot have a sub-5% debt:

• allocate efficiently sub-5% debt

Putting the above two conditional diagrams together, we get the following:

• Centrally planned economy allocate efficiently sub-5% debt

This supports the author's conclusion, that:

• Centrally planned economy sub-5% debt

The correct answer choice follows the same logic:

• Rural district large concentration of cars major air pollution

...drawing a similar inference:

• Rural district major air pollution

I hope that's helpful! Please let me know whether this is clear—thanks!

~Steve

[Sherry001]

Super clear. Thank you so much !


Sherry

[al_godnessmary]

Okay, so...I got the question stem diagramming right, and this is what I ended up with:

GDP less than 5% efficient allocation of resources —central planning

Therefore the contrapositive being:

central planning —efficient allocation of resources —GDP less than 5%

So far so good.I also managed to eliminate A, D and E without much difficulty, and then this is where I got stuck.

This is how I diagrammed B:

rural districts —major air pollution (All rural districts are free of major air pollution problems)
major air pollution auto concentration ( major air pollution problems occur only where there is a large concentration of automobiles)
rural districts —auto concentration (there are no places of high automobile concentration in rural districts)

Clearly I reversed my conditions at some point. But how?!

So in any case, I settled for C because this is what I thought:
U H —attack

Contrapositive (since I took the contrapositive of my stem diagramming):
attack H U (I took "unlikely to be" as "chances less than 50%" so reasoned that the would work for this case)

How should I have interpreted answer choice B to diagram it correctly?

[Emily Haney-Caron]

Hello!

Great question. The thing that trips people up about B is that the conclusion actually comes FIRST; you're connecting the two statements that come after "because" to reach the conclusion at the beginning of the sentence.
Conclusion: rural air pollution problems
air pollution problems lots of cars
rural lots of cars
Taking the contrapositive of the second one, we have: lots of cars air pollution problems
That gives us this chain:
rural lots of cars air pollution problem

This is the same reasoning as the stimulus; essentially, we have A B, B C, therefore A C. We had to take some contrapositives to get it, but that's the basic structure.

C here you don't actually need to diagram; most tells you it is not going to be the right answer, as it makes it not the same type of reasoning as our argument.

[al_godnessmary]

Wow, I can't believe I missed that - I had all the parts diagrammed correctly but I didn't see that I could have connected them that way. Thanks!

[silent7706]

Hi,

I crossed off (D) quickly because its conclusion says, "This implies...." , which I felt had a different level of certainty compared to "It follows...". from question stimuli. I just want to confirm whether "implies" and "follows" are indeed on a different certainty level.

Thanks in advance.

[James Finch]

Hi Silent,

No, "implies" also could refer to an inference (such as the A C inference made in the stimulus that we need to parallel). The real issue with (D) is that it does a bait-and-switch with terms in the conclusion, where the stated "C" in the
A C chain isn't the same one given by the premises: "company profits over and above regular royalties" shifts to "large regular royalties," not the same thing at all.

Hope this clears things up!