October 1996 LSAT Section 4 Question 19

Nearly all mail that is correctly addressed arrives at its destination within two business days of being sent. In fac...

AndrewArabie on February 15, 2023

I need more help rationalizing the correct answer than the video provides

Would a correct answer also be "A large proportion of mail is damaged in transit"? For me I would think its incorrect if I came across it but I can't explain why its incorrect based solely on our logic chains. The only logic I can give is that it's probably more likely for mail to be incorrectly addressed than damaged in transit but that would be speculation beyond the limit you should speculate on the LSAT. I ruled many of the answer choices based on the idea we have no idea how much mail is correctly addressed and how much is incorrectly addressed. Without knowing that we are really limited in what we can say is true but let's say most mail is correctly addressed, and all correctly addressed mail is damaged in transit then it must be true large proportion of the mail is damaged in transit. I don't know there's something about this question and answer choice that my understanding is still shaky on.

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AndrewArabie on February 15, 2023

I guess my problem is that I don't feel comfortable severing correctly addressed, undamaged mail from correctly addressed, damaged mail in the answer choice.

Emil-Kunkin on February 16, 2023

Hi, we actually do know something about the proportion of mail that is correctly addressed. We know that most mail arrives late. There are two ways to be late, either to be incorrect or to be damaging in transit. We also know that the vast majority of correct mail does not arrive late. So, we must know that quite a lot of mail must not be correct. I don't think it has to be true that a lot of mail is damaged. Perhaps no incorrect mail is damaged, and the only mail that is damaged is that which is correct.

AndrewArabie on February 18, 2023

Looking at this question again, I've made one deduction I did not make before:
If most correctly addressed mail arrives within two business days, and it only takes longer than this if it was damaged, that means most correctly addressed mail is not damaged.
I've gotten this far, but I still can't understand why it must be true that most mail is incorrectly addressed. I would be more comfortable with the correct answer if it said "most mail is incorrectly addressed or damaged in transit." Could you go into more detail?

Emil-Kunkin on February 22, 2023

So I think the deduction that "most correct mail is not damaged" is correct, but there is another critical one, that most late mail is late because it is incorrectly addressed, not because it was damaged. Since most late mail is late because it was incorrect, we can then safely say that quite a lot of mail is incorrectly addressed, since we know that most mail is late.

Not that I'm not saying most mail is incorrectly addressed. We actually don't know for sure if it's most, or just a significant proportion. However, since we know more than half Is late, and the vast majority of late mail is incorrect, then we know that a lot (At least roughly a third, probably more than that) is incorrect.

Emil-Kunkin on February 22, 2023

AndrewArabie on February 22, 2023

Thank you Emil. I think Im catching on.