Q16 - At the end of 1997 several nations stated that their

[ccheng]

I would really appreciate if someone could explain why B is correct, not C. I was debating between them. Here is my understanding.

Argument:
Premise1 = Several nations stated that their oil reserves had not changed in 1997.
Premise2 = Author provides his response by saying oil reserves fluctuate (drop as old oil field are drained and rise as new oil fields are discovered).
Premise3 / intermediate conclusion = Oil reserves are unlikely to remain unchanged from one year to the next.
Conclusion = Most of the nations stating that their oil reserves were unchanged are probably incorrect.

A few things are worth noticing in the argument. First, author changes from "several" to "most" nations. Second, premise1 is about the oil reserves within a single year but author's response is about the oil reserves between years.

Both choices B and C are tempting.
Choice B points out the gap between premise1 "several nations" and conclusion "most nations". When we negate B as ~(drain or discovered or both), it becomes none. In other words, when most nations said their oil reserves were unchanged and their oil fields were not drained and no new discovery, this destroys the conclusion.

When we negate choice C, it becomes "the oil reserves of at least one nation did not gradually dropped or rise suddenly. This allows the possibility that one or both conditions exist and hence does not destroy the conclusion.

Appreciate any comments.

[jblim1324]

Between A and B,
the logical negation of A is not "it is less likely that the nation..." but "it is not more likely that the nation was mistaken in its statements about changes in oil reserves than that the nation's oil reserves remained unchanged".

So when you negate A, it could be either that "it is just as likely that the nation was mistaken in its statements as that the nation's oil reserves remained unchanged" or that "it is less likely that ....".
I don't think that the former ("it is just as likely...") really hurts the original argument so, in order for the negation of A to hurt the original argument, you have to make an additional assumption that it's the latter ("it is less likely").

In contrast, the negation of B ("it is unlikely that, in most of the nations that stated that their oil reserves were unchanged, old oil fields were drained or new oil fields were discovered") counters the premise of the argument, which says that oil reserves are unlikely to remain unchanged from one year to the next.

I wrote this in a rush so there may be a mistake here and there in what I said, but my main point, as well as the reason that I got this one wrong, is that the negation of "more likely" is not "less likely" but "not more likely," which could be either "just as likely" or "less likely".

[maryadkins]

When we negate choice C, it becomes "the oil reserves of at least one nation did not gradually dropped or rise suddenly. This allows the possibility that one or both conditions exist and hence does not destroy the conclusion.

It doesn't need to be true (i.e. it doesn't destroy the conclusion) because we don't need both to have happened. We do need one to have happened, which is why (C) could be tempting.

I wrote this in a rush so there may be a mistake here and there in what I said, but my main point, as well as the reason that I got this one wrong, is that the negation of "more likely" is not "less likely" but "not more likely," which could be either "just as likely" or "less likely".

Thanks for clarifying this!

As for the two answer choices that haven't yet been addressed:

(D) kind of restates what the argument is, but without filling in the gap. The whole point is we don't KNOW if the nations incorrectly stated they hadn't changed. So telling us "if" they did or not doesn't tell us if they did or not.

(E) makes it a moral thing and that's not it...we aren't talking about obligations.

[Vivi]

Could any LSAT Geek weigh in on this question from an overall perspective?

Some tempting questions include but not limited to 1) why in such a NA question, the weak answer like C "at least one" lost to B (likely, "most") that seems stronger worded? 2) besides negation, is there any other more direct way in arriving to the right answer? 3) It might mislead, if some of the above negation seems incorrect, such as the version of negation C (at least one not = not some=.....) ------ would be great to confirm the corrected negation of C and how the then corrected negation of C works with the conclusion?

Many thanks! Look forward to your advices.

[christinachenn]

I am not an LSAT geek, but this is my evaluation of this question.

Premise: Oil reserves drop and rise etc. so oil reserves are unlikely to remain unchanged from one year to the next.
Conclusion: Most nations that stated their oil reservers were unchanged from end of 1996 to end of 1997 are probably incorrect.

The assumption here is that the premise conditions would actually apply to "most" of the countries that are claiming their reserves have not changed. If the premise conditions (either reserves dropped or rose, or both...doesn't matter because each or all of these means reserves changed) did not apply to the countries, they would not be incorrect.

Answer B speaks to this assumption. Also, notice how it is the only answer choice to reference the "most nations" that is stated in the conclusion. If you negated it, it would say "It is NOT likely that oil fields were drained, discovered, or both in most of those countries that stated their oil reserves were unchanged." If this negated answer is correct, then the nations are correct and the argument is wrong.

Answer A negated would say "For any nation with reserves, it is just as likely that it was mistaken than that their reserves were unchanged." This doesn't kill the argument.

Answer C simply doesn't need to be true as was mentioned in an earlier response. For a nation's reserves to be changed, at a minimum, you just need the reserves to have either risen or dropped.

Answer D is not necessary because it's making a statement using the author's conclusion, and also because if a country is incorrect, it doesn't need to have done both draining and finding new ones. It could also not have done any of those!

Answer E is out of scope for me. I don't see where an obligation to report correctly was ever mentioned.

[tommywallach]

Vivi, let me know if you need more, or if Christina's (awesome) response got the job done!

-t

[maria487]

Just an addendum to the previous explanation for this question, I think A is incorrect because it is too broad in addressing "any nation w/ oil reserves".

If its scope was narrowed to "any nation of those which stated that their reserve level had not changed" then it would be correct. If I'm not mistaken, the argument is assuming that it is more likely that the countries which reported no change were mistaken than that their reserves were actually unchanged. I think that my proposed change of scope would actually make the answer choice a paraphrased version of B--which states that it is likely that in most nations w/ reported unchanged oil reserves, there actually were changes.

[cacrv]

Just an addendum to the previous explanation for this question, I think A is incorrect because it is too broad in addressing "any nation w/ oil reserves".

I agree with this; and in the same line of reasoning, I think that C is also wrong because of this number factor. If the speed of the change in oil levels was relevant in this question, C would still be wrong because it could be the case that this applies to only one nation, while the stimulus specifies most nations making this incorrect claim. Is this correct? I'd appreciate any corrections or confirmations, thanks!

[donghai819]

Hi teachers,

While Christine‘s explanation is very helpful, one that still confuses me is the word "likely" in B. TBH, if the "likely" is not here, I would definitely have picked B. Is the use of "likely" viable here because the "unlikely" is used in the original argument? Or it would OK to use "likely" in this word without any "notable subtlety" (I hope the phrase I made up makes sense here). Additionally, the "likey" confuses me in two ways: I was unable to negate a sentence with "likely", and I also overthought about the role that "likely" played is to rule out a very plausible answer choice. Can any teacher lend me a hand?

[contropositive]

Hi teachers,

While Christine‘s explanation is very helpful, one that still confuses me is the word "likely" in B. TBH, if the "likely" is not here, I would definitely have picked B. Is the use of "likely" viable here because the "unlikely" is used in the original argument? Or it would OK to use "likely" in this word without any "notable subtlety" (I hope the phrase I made up makes sense here). Additionally, the "likey" confuses me in two ways: I was unable to negate a sentence with "likely", and I also overthought about the role that "likely" played is to rule out a very plausible answer choice. Can any teacher lend me a hand?

I am not a teacher but hopefully I can help you. the word likely is actually one factor that makes answer choice B correct. The conclusion reads, "so most of the nations stating that their oil reserves were unchanged are PROBABLY incorrect". Therefore, B is playing on the safe side by saying "likely".


The core is:
Premise: oil reserves either drop as old oil are drained or rise suddenly as new oil fields are discovered
Int. Conclusion: oil reserves are unlikely to remain unchanged
Conclusion: most of the nations claiming their oil reserves were unchanged are probably wrong

Assumption:most of these nations experienced a drop as old oil were drained or rise as new oil fields were discovered


A) it seems like A is weakening the argument because it says "the nation was mistaken about changes" when we just learned that changes are likely

C) the argument was more in a sense of "either/or" so this one is saying it had to have both

D) we don't know what happens once the conclusion is triggered

E) obligation is out of scope

[ohthatpatrick]

GREAT response, thanks!

Many of us are well-trained to beware strong language in Necessary Assumption (and Inference and Reading Comp).

But this isn't an absolute prohibition. We're saying, "strong language is a red flag ... don't pick an answer that has strong language until you've found wording in the argument/passage that would justify that strong language".

For example, the correct answer to Necessary Assumption is usually not of conditional strength, but it's allowed to be if the author's conclusion is CERTAIN.

f.e.
Dave is left-handed. Thus Dave must be clumsy.

Both of these would be correct necessary assumptions
(A) Some left handed people are clumsy
(B) All left handed people are clumsy

We're allowed to pick both (A) and the more extreme-written (B) because our author thinks "knowing Dave is left-handed is SUFFICIENT to GUARANTEE us that Dave is clumsy."

So the author is assuming a constant, inflexible connection between those ideas, one that leaves no room for exceptions.

Meanwhile, if the argument were
Dave is left-handed. Thus Dave is probably clumsy.

Then (A) and (B), but NOT (C) would be correct necessary assumptions
(A) Some left handed people are clumsy
(B) Most left handed people are clumsy
(C) All left handed people are clumsy

The strength of the conclusion is LIKELIHOOD, not CERTAINTY.

CERTAINTY = all, no, none, always, must, only, unless, can't, etc.

LIKELIHOOD = most, probably, likely, tends to, generally, usually, a majority

POSSIBILITY = can, might, may, sometimes, some, not all, need not

If you ever are struggling with how to negate something, just put the phrase "It is NOT true that _____ " in front of the answer.

Or, more mathematically, "likely" means "greater than 50% chance". So negating that means, "0 to 50% chance".

I would generally just cheat a little and negate "likely" as "unlikely". Technically doing that involves omitting the possibility that it's 50% (which is neither likely nor unlikely), but it's extremely unlikely that the 50% scenario would matter.

So you can "fake negate" words like
"most" vs. "few"
"usually" vs. "rarely"
"likely" vs. "unlikely"
(more than half the time) vs. (less than half the time)

But the real way you check whether an extreme word is safe for a given question is just to look at the strength of wording in the conclusion.

PROBABLY = LIKELY, so we're good to go with that part of (B).

[ganbayou]

I elminated C because the conclusion says most, and C is about at least one nation...is my reasoning correct?
C uses the words from the stimulus (gradually dropped) (rose suddenly) so it was tempting but I guess they chose the words wrong because they are not the focus in this argument?

[mshinners]

At the end of 1997, several nations said their oil reserves hadn't changed.

+

Because oil reserves gradually drop when they're drained and rise when new fields are discovered, they're unlikely to stay the same

-->

Most of the nations claiming no change were probably wrong

But why must these "several" nations be among the nations where there was a change? In other words, just because a change is likely doesn't mean that it happened to the handful (could be3?) nations who said they had no change.

(A) is too extreme for this necessary assumption question. "For any nation" is our cue.

(B) is correct. It bridges our conclusion to our premises by telling us that these very nations we are concerned with experienced the conditions that lead to changes.

(C) is like (A), too extreme. We don't need the oil reserves of any nation to have both fallen and risen; we DO need the oil reserves of at least one nation to have changed, but they did not then need to change back.

(D) presumes in its condition what the conclusion here is arguing. "If a nation incorrectly stated..."? We don't know if it did incorrectly or not; that's the point. It's also too broad with the use of "If a nation..."

(E) is out of scope. Obligation?

[andrewgong01]

I think "B" required the additional assumption that "Gradually drop" and "Suddenly rise" will never perfectly off set each other. My pre-phase was on my paper "No offset" and 1996 estimates were not wrong

The issue I had when I first did the problem was that if we went with "B" we are saying that countries may have 1) Drained more oil 2) Found new Oil 3) Both

but the "Both" option would entail assuming Barrels of Oil Drained does NOT equal Barrels of Oil Discovered in order for "B" to hold. My guess is that the LSAT "gets around this " by saying "gradually" and "suddenly" but I still feel that there was a slight jump in logic and the reason why I was hesitant at first with "B"

For "A" I didn't rule it out on that basis above ("For any nation"= too strong) because I thought the more fundamental issue with "A" is more so that just because something is more likely to happen (making a mistake) is not enough in the argument to be necessary because if we say choosing "A" is correct we are choosing it on the principle/assumption that something more likely to be true is indeed more likely to be true. And something less likely to be true does not destroy the reasoning of the argument, albeit it does weaken the reasoning more