LR Question 24 Explanation
QUESTION TEXT: Paleomycologists, scientists who study ancient forms of…
QUESTION TYPE: Flawed Parallel Reasoning
CONCLUSION: Professor Mansour must be a paleomycologist.
M ➞ PM
REASONING: Paleomycologists know about the writings of other paleomycologists. Professor Mansour knows the writings of one paleomycologist.
ANALYSIS: This argument confuses necessary for sufficient. Yes, all paleomycologists know about paleomycology. That doesn’t mean that anyone who knows about paleomycology is a paleomycologist. The argument incorrectly reversed this: PM ➞ M
The argument makes a second error. The necessary condition is that paleomycologists know about the writings of all other paleomycologists. Professor Mansour only knows about the work of one paleomycologist: Professor DeAngelis. The right answer should match both of these flaws.
___________
- CORRECT. This repeats both flaws. The premise: Flight delayed ➞ all connecting delayed
The argument reverses this to: one connecting delayed ➞ original flight delayed
They also shift from ‘all connecting flights’ to ‘one connecting flight’.
(By the way, the first flight is not a connecting flight. Connecting flights happen after an initial flight. I’m mentioning this in case you thought a delay on a later flight would guarantee delays on earlier flights.) - This is a bad argument, but it makes a different error. Here, the conclusion negates the sufficient condition of the premise, and assumes that the necessary condition is negated.
M ➞ WH,M➞WH - This is a good argument. If expenses decrease and income stays the same, profit goes up.
- This is a bad argument, but it makes a different flaw. We only know Gavin can participate in the plan. That doesn’t mean he will do it.
- This is a bad argument, but it makes a different error. If a competitor dropped prices, then it’s true that Global must have done the same. But, we don’t know whether a competitor did drop prices.
More Resources for Flawed Parallel Reasoning Questions
- Conditional Reasoning Article: Learn about conditional statements.
- LR Diagrams Guide: Learn how to draw LR diagrams.
- Flaw drills: Practice identifying flaws.
- Intro Course lesson: This intro course lesson covers Flawed Parallel Reasoning questions.
- Mastery Seminar lesson: This LR Mastery seminar lesson covers flawed parallel reasoning questions.
I don’t see how the argument makes a second flaw. The argument doesn’t state that Prof. Mansour “only” knows Prof. DeAngelis. It states that he knows of a certain Prof. DeAngelis. One cannot infer that he does not know of any other paleomycologists. Just because a single paleomycologist is mentioned by name, doesn’t imply Mansour is unfamiliar with all other paleomycologists.
p.s. Your website has been very helpful in my LSAT study.
I don’t get how D isn’t the same flaw. .
“D. This is a bad argument, but it makes a different flaw. We only know Gavin can participate in the plan. That doesn’t mean he will do it.”
It mistakes that because Gavin can, he will
necessary for sufficient.
Hi Bill,
In (D), the argument would parallel the stimulus if we said:
All employees of Global Airlines who have been with the company a year or more are INVARIABLY participants in all available benefits programs. Gavin participates in the 401 (k) contributions program, and therefore he must have joined the company at least a year ago.
The argument in the stimulus is flawed in that it confuses sufficient for necessary as well as some for all. The argument in (D) is flawed, but not quite in the same way. They both misunderstand a sufficient condition, but they don’t share an identical flaw. (A) does!
Hope that helps!
Answer choice C actually represents a bad argument. Its conclusion states that there must have been a profit in that year, but the premise says that when fuel prices decrease, the expenses also decrease while the income remains the same. It is not known whether anything else might have affected the profit, but that’s not the main problem. We don’t know if there was a profit to begin with. Maybe it’s a losing company, its starting point is a huge loss anyhow. Decreases in fuel will improve its condition, but they do not assure us that the company will make a profit. It might still be losing lots of money.
Hi Asaf – You’re right, (C) doesn’t really prove that there’s a profit, but the flaw is just a simple assumption that decreased costs + same revenue = profit, and in some cases this isn’t true. It’s a very different flaw than the one being made in the stimulus!
Thanks for your comment!