#20 - Only experienced salespeople will be able to meet the

[Administrator]

Complete Question Explanation

Parallel Flaw. The correct answer choice is (B)

The first statement presented in this stimulus is that only experienced salespeople will be able to meet the company’s selling quota. In other words, if you are going to meet the company’s sales quota, then you must be an experienced salesperson:

• quota experienced salesperson

The writer concludes that if one doesn’t achieve the quota, one must not be an experienced salesperson:

• quota experienced salesperson

This is a clear case of Mistaken Negation. We are asked which answer choice reflects the flawed pattern of reasoning in the stimulus, so the correct choice will be the one which reflects an analogous Mistaken Negation.

Answer choice (A): The first conditional statement provided here is that employees are allowed to dress casually only on Fridays. The author of this answer choice concludes, based on Hector’s formal dress, that he must not be going to work. The reasoning contained in this answer choice is flawed, because Hector might still go to work on Friday, and opt out of the casual option. This is not a Mistaken Negation, however, so this choice does not parallel the flawed reasoning found in the stimulus.

Answer choice (B): This is the correct answer choice. This answer choice offers a conclusion based on a conditional statement:

• Premise: Only music lovers take this class.
  
  Flawed conclusion: Since Hillary’s not taking the class, she’s not a music lover.
  
  
  Premise: take class music lover
  
  Flawed Conclusion: take class music lover

This flaw is the same as that found in the stimulus: Mistaken Negation.

Answer choice (C): This answer choice provides the following conditional reasoning:

• Premise: Only oceanographers enjoy the Atlantic in midwinter—that is, if you enjoy the Atlantic in the midwinter, you must be an oceanographer.
  
  Conclusion: Since Gerald is not an oceanographer, he can be expected not to enjoy the Atlantic in midwinter. This valid conclusion is the contrapositive of the conditionally stated premise.

The above can be diagrammed as follows:

• Premise: Enjoy Atl MW oceanographer
  
  Valid Conclusion: Oceanographer Enjoy Atl MW

Since the conclusion above is a valid contrapositive of the original statement, this sound reasoning cannot parallel the flawed reasoning reflected the stimulus.

Answer choice (D): This answer choice presents the following conditional reasoning:

• Premise: It is only in the northern latitudes that we would find giant redwoods; that is, if we see a giant redwood, we must be in the northern latitudes.
  
  Conclusion: We are looking at a giant redwood, so we must be in the northern latitudes.

As we can see, the above conclusion represents a restatement of a conditional rule:

• Premise: Redwood Northern latitudes
  
  Conclusion: Redwood Northern latitudes

Since this choice is based on sound reasoning, it cannot parallel the flaw in the stimulus.

Answer choice (E): This answer choice reflects the following flawed conditional reasoning:

• Premise: Only accomplished mountain climbers can scale El Capitan; that is, if one can scale El Capitan, that person is an accomplished climber.
  
  Conclusion: Since Michelle is an accomplished climber, she must be able to scale El Capitan.

The reasoning in this answer choice is flawed, but it is not a mistaken negation, as we can see when we diagram the above conditional statements:

• Premise: EC AMC
  
  Conclusion: AMCM ECM

This is a Mistaken Reversal, rather than a Mistaken Negation. Because this answer choice does not employ the same pattern of flawed reasoning as that reflected in the stimulus, this answer choice should be eliminated.

[Sherry001]

Hello;
For this super easy question I had trouble identifying between B and C. What did I do wrong? usually I am pretty good at identifying suffciant and necessary indicators but I do not know where I went wrong with C.


Meet Quota -> Experienced
not meet quota -> not experinced

B) Class -> Music lover
not take class -> Not music lover

C) Enjoy winter -> Oceanographers
Not enjoy winter -> not oceanographers -

Thanks so much!
sherry

[Dave Killoran]

Hi Sherry!

Thanks for the question. You've got everything right except for your analysis of answer choice (C). They changed the order of the argument parts in the second sentence, and that looks like it threw you off. Let's take a closer look:

With answer choice (C), you've diagrammed the first sentence correctly (good job!). But, they pulled a little trick with the second sentence: the conclusion is given first, and then premise. So, (C) is a contrapositive and actually looks like:

• Answer choice (C):
  
  Enjoy winter Oceanographers
  
  Oceanographers Enjoy winter

That's a fairly common trick they use, so it's a good thing to come across is while still studying. To really lock in this idea, take a look at the differences in the second sentences of (B) and (C).

• Answer choice (B):
  
  "Thus, since [premise], [conclusion]."
  
  
  Answer choice (C):
  
  "Thus, [conclusion], since [premise]."

That little ordering change made a big difference in how you read answer choice (C), and caused the confusion here. So, make sure you are comfortable with what they've done here because you will see it again

Please let me know if that helps make this one clear. Thanks!

[lilRio]

Dear Powerscore,

In evaluating answer choice (C), how do I know which is my sufficient condition and my necessary condition in the second sentence of the answer choice? "Since" and "Thus" are premise and conclusion indicators, but are they being used here as sufficient and necessary indicators? Thank you for your time and consideration.

-MMM

[KelseyWoods]

Hi lilRio!

That's a great question! When an LSAT author makes an argument, they're essentially saying that their premise(s) are enough (or sufficient) to prove their conclusion. They're basically saying "if this premise is true, then this conclusion is true." So you can think of the premise in an LSAT argument as being sufficient to prove the conclusion.

This doesn't mean that you need to use conditional diagramming for every LSAT argument that you encounter. But when you have an argument that presents you with conditional rules, it's important to also realize that the author is saying that the premise is sufficient for the conclusion so that you can diagram it accordingly.

Hope this helps!

Best,
Kelsey

[lilRio]

Dear Kelsey,

Yes, it helps. Thank you for your response.

[sdb606]

This is a Mistaken Reversal, rather than a Mistaken Negation. Because this answer choice does not employ the same pattern of flawed reasoning as that reflected in the stimulus, this answer choice should be eliminated.

A mistaken negation and mistaken reversal are logically equivalent so how could E be wrong? Seems like both B and E should be right.

[Robert Carroll]

Samuel,

That's a good question. The short answer is that Mistaken Reversal and Mistaken Negation are logically equivalent, but that doesn't mean that arguments involving them are identical in form.

I think building to that point from a distinction you'd probably agree with would help. So, take the following two arguments:

1. Anyone who passes the qualifying examination will be exempted from the logic requirement. Aaron has passed the qualifying examination. Therefore, Aaron is exempted from the logic requirement.

2. Anyone who receives a GPA over 3.7 will receive departmental honors in the graduation ceremony. Beth did not receive departmental honors, though the graduation ceremony was just completed. Therefore, Beth did not receive a GPA over 3.7.

Diagramming:

1. pass QE exempt from logic
pass QEAaron
exempt from logicAaron

2. GPA over 3.7 honors
honorsBeth
GPA over 3.7Beth

These are both valid arguments. We'd describe the former as using the conditionally normally, and the second as involving a contrapositive. If the stimulus for a Parallel Reasoning question involved an argument that matched 1, we wouldn't pick an answer matching 2, or vice versa. I think that's something we all agree on, and probably don't even think about, but when made to think about it, we should agree. So we recognize that these arguments are different from each other in logical form.

Now look at two flawed arguments:

3. Anyone who skips more than 3 labs will fail the course. Carl failed the course. So Carl skipped more than 3 labs.

4. Anyone who works at the campus bookstore is permitted in the Bollman Center after 8 PM. Dana does not work at the campus bookstore. Therefore, Dana is not permitted in the Bollman Center after 8 PM.

Diagramming:

3. skip 4+ labs fail
failCarl
skip 4+ labsCarl

4. work at bookstore BC late
work at bookstoreDana
BC lateDana

The distinction between 3 and 4 looks a lot like the distinction between 1 and 2. But 3 is a Mistaken Reversal and 4 a Mistaken Negation. So if 1 and 2 are different, then 3 and 4 are different. So, for a Parallel Flaw question, a Mistaken Reversal and Mistaken Negation don't match.

To make this more clear, if needed, note that 1 and 2 are different because 2 has an unstated assumption: "From a conditional that says S N, you can infer a conditional that says N S". That unstated assumption is a valid inference, so its existence doesn't infirm the validity of the argument. With that assumption, the contrapositive just works like a normal conditional - the sufficient condition of the contrapositive is just the second premise of the argument, so the argument goes through like a "normal" conditional.

3 and 4 differ in the same way. 4, but not 3, requires a contrapositive. A contrapositive of what? Well...3 and 4 both rely on an unstated assumption: "From a conditional that says S N, you can infer a conditional that says N S". That's a mistake! So Mistaken Reversal and Mistaken Negation make the same mistake, but the way an argument uses Mistaken Negation is to take that mistake, add the assumption "From a conditional that says N S, you can infer a conditional that says S N", and go forward like a "normal" conditional. Note that assumption I just quoted is not a new mistake. Once 4 infers the Mistaken Reversal, like 3 did, contraposing that is not a new mistake. It's one more assumption than 3 makes, which is why 3 and 4 differ, but the only mistaken assumption of 4 is the same one 3 makes. So MR and MN are the same mistake, but arguments using them differ, just like arguments using a conditional normally and a contrapositive are different.

Robert Carroll