LSAT 147 | Section 4 | Logical Reasoning: Q12

LR Question 12 Explanation

QUESTION TEXT: West: Of our company’s three quality control…

QUESTION TYPE: Method of Reasoning

ARGUMENTS: West says that Haynes is the worst quality control inspector because more than half of the company’s defective items had been inspected by Haynes.

Young points out that Haynes inspected significantly more than half of the items.

ANALYSIS: Young raises a good point: we care about error rate, not error number.

Let’s say you took all of the LSAT preptests (89 at the time of writing). You make one error on each, scoring an average of 180 on each test. You have 89 total errors.

Your friend takes two LSAT preptests. They make 80 errors between the two tests, scoring an average of 150 on each test. They taunt you “haha, you made a greater number of mistakes than me!”

Does that bother you? Of course not! You got 180s: you had a low error rate. Same thing with Haynes. They inspect a massive amount of items. So even if they have a tiny error rate, their absolute number of errors is high. But that doesn’t matter at all: their rate is low.

What Young is doing is contradicting an assumption West made. West had assumed that Haynes didn’t inspect that many appliances, and therefore their error rate was high.

___________

1. This describes circular reasoning. That didn’t happen here.
    
   Example of circular argument: Haynes is bad because he is Haynes.
2. If a quality control inspector is bad at controlling quality, that is very relevant.
    
   Example of irrelevant conclusion: I hear Haynes likes to collect stamps. I worry what this says about his quality control skills.
3. This is a trap. Young didn’t contradict a premise. Instead, he added new information that makes us view the argument in a different light.
    
   Example of contradicting a premise: Actually, far less than half of the items returned had been inspected by Haynes.
4. This didn’t happen.
    
   Example of weaker conclusion: Haynes is clearly not a great quality control inspector, even though he is far from our worst.
5. CORRECT. This matches. Presupposition = unstated premise. In this case, West is assuming that each inspector inspected similar amounts of items. Once we know Haynes inspected more than half, we see they actually have a better than average error rate.
    
   This is right and C is wrong because the argument didn’t explicitly state the presupposition.