Q24 - The Kiffer Forest Preserve...

[noah]

The core of this argument is this:

Over past 8 years during road closure, the bear population in Preserve has increased --> bear population in the Valley will continue to increase if road stays closed.

Seems sensible, but we know that we can debate this and find a gap - how else will the LSAT come up with a weaken question? Note the shift in the argument: in the premise we learn about the population increase in the Preserve , but in the conclusion it's all about the entire Valley (remember, the Preserve is just one part of the Valley). Hmmm. That's like saying: there are more rich people in NY now than there were ten years ago because of the new tax breaks, so if we continue the tax breaks, there will be more rich people in the world. Couldn't it be that the rich people just moved to NY and the number of rich people in the world will not change?

(E) is confusing - but it plays on the shift mentioned above. According to the stimulus the population in the Preserve increases, but the population in the Valley, according to (E), remains the same. How could this be? It must mean that bears are moving from other parts of the Valley to the Preserve section. So, (E) suggests that the bears simply moved into the preserve from the surrounding area.

(A) - (D) don't undermine the idea that the general bear population in the Valley will continue to increase.

(A) gives us a reason why the population of the Preserve has increased, and that migration could continue.

(B) actually strengthens the argument. One could take this to mean that the increase is not only because of local migration; it might, for example, be that the bears are having more kids now that folks aren't watching them. Or maybe bears are coming in from faraway places, which might continue...

(C) suggests that only a part of the increase is from external migration. This could strengthen the argument since we could take that to mean the rest of the increase is from more cub-making activity.

(D) is tempting. It seems like it's suggesting that perhaps the bears have moved from other local areas into the Kiffer Preserve. But all it actually says is that there are less bears outside the Preserve. Movement is only one explanation for why there are less bears outside the Preserve and we don't know it's the correct one.

#officialexplanation

[clarafok]

could someone elaborate a little bit? i hesitated to choose E because the argument said that the population increased 'during the 8 years', i thought E contradicted that by saying the population remained the same over the past 8 years. aren't they talking about the same 8 years?

thanks in advance!

[noah]

Note the detail creep: the population in the Preserve increases, but the population in the Valley, according to (E), remains the same. (And the Preserve is one section of the Valley). How could this be? It must mean that bears are moving from other parts of the Valley to the Preserve section.

I edited my explanation above, as i realize i didn't make this clear, nor focus on the detail creep between the premise and conclusion.

Does it make sense now?

[nflamel69]

This question is confusing as hell. At first I thought of the same thing, maybe it's just because bears moved from one area to another while the total didn't change. When I saw E it did match the total didn't match part, but it didn't explicitly say its because bears moved from one place to another... I just had to choose it because it was the only one that allows me to infer that.

[sch6les]

Main road being closed correlated with increase in preserve bear population
---
Therefore, main road being closed causes increase in valley bear population

There are two assumptions being made here:
(1) preserve bear population => valley bear population
(2) correlation => causation

(E) is basically negating (1). It tells us that what happens to the preserve bear population is not an accurate indicator of what happens to the valley bear population. It does this by telling us that during the past 8 years, the valley bear population did not increase, even though the preserve population did.

[oceangirl182]

I got this question right, but I took a little time deciding between A) and E). The reason I wasn't sure that A) was wrong was because I thought it was talking about the same sort of idea as E--that most of the increase in the preserve is due to migration (from the rest of the valley).

I ultimately picked E) because it sort of implied this more strongly, but guaranteed that the migration was occurring within the valley into the preserve and not from outside the valley. Still, I find the difference to be rather subtle, at least the way that I'm interpreting it! Did anyone else think these two were close?

[cyt5015]

Answer A can go two directions weaken and strengthen, depending on the location bear migrating from. If bear migrate from rest of the Valley, then it does undermine; if bear migrate from other place outside of the valley, then it strengthens. We can't choose an answer playing an ambiguous role.
Additionally, "Only some" in answer B and C does not mean "only a small portion of bear", because some can range from 1 to 100, given that 100 means all.

[aznriceboi17]

This doesn't affect the correct answer choice, but how exactly is the 'only some' in (B) and (C) supposed to be interpreted?

Normally, 'some' can indicate a quantity from one to all (this link was helpfor http://www.manhattanlsat.com/blog/tag/quantity/).

However, if it is modified with 'only', does that imply that the MAX possible is no longer ALL? If the 'only' is to serve any function, it seems like 'only some' excludes ALL, i.e. should mean 'some, but not all'.

[christine.defenbaugh]

This doesn't affect the correct answer choice, but how exactly is the 'only some' in (B) and (C) supposed to be interpreted?

Normally, 'some' can indicate a quantity from one to all (this link was helpfor http://www.manhattanlsat.com/blog/tag/quantity/).

However, if it is modified with 'only', does that imply that the MAX possible is no longer ALL? If the 'only' is to serve any function, it seems like 'only some' excludes ALL, i.e. should mean 'some, but not all'.

Excellent work, aznriceboi17!

That's exactly how the phrase 'only some' works! It limits the 'some' quantity and explicitly distinguishes it from 'all'.

So, in practice, 'only some' might be thought of as giving you two pieces of information: some are AND some are not! The second one is not a leap we are able to make from the word 'some' alone!

Bravo!

[peterbobolis]

While I like Noah's explanation for (D), this initial explanation may have contributed to the confusion:

"(E) is confusing...Preserve increases...Valley.... remains the same. ...It must mean that bears are moving from other parts of the Valley to the Preserve section..."

Not necessarily; could bears not move into the preserve from outside the valley, passing those leaving the valley outside the preserve on their way?

This possibility is especially real given the preserve's (subtle) location at the northernmost part of the valley...so bears could conceivably enter the preserve without ever stepping paw into the valley outside the preserve (unless the northernmost boundary has a bear stepping off the edge of Earth :b )

"maybe the bears are done migrating around the Valley and thus the population increase might be over."

migration considerations etc are all unnecessary and go too far...

Premise: More bears inside Preserve now; Preserve inside Valley.

Conclusion: Will be more bears in Valley.

More simply, the road closure and even the Preserve are red herrings and could be ignored. (E)'s weakener isn't very weakening, the other answers garbage.

LSAC's part to whole test is a smokescreen; some part of the valley's number increased recently...so the valley's number will increase...the best of all the imperfect answers is E; recently the number hasn't increased (so we cast some doubt on it increasing)...weak weakener

[coco.wu1993]

I did this one correct, but I think E is a bit strange. The stimulus says most of the bears in the valley reside in the preserve. According to E, the bear population in the valley has remained the same during the past 8 years. Then only in extreme circumstances can we say the preserve's bear population has nearly doubled.

Say, the valley has 100 bears and the preserve owns 51 of them (majority). Over the 8 years, the bear population in the valley has remained the same (100). The preserve's bear population at most can reach 100, so we can say it nearly doubled (almost 102).

Just some random thoughts...

[contropositive]

I think the test writer really wanted to play with our minds when they didn't capitalize the Preserve and Valley. By writing it in small caption it makes one read fast and think the author is talking about the same area and immediately eliminate E because it seems to question the validity rather than reliability of the premise. They typically capitalize a word if they are referring to a particular subject/area. smart move

[olaizola.mariana]

Noah, I have a question:

If this had been a "strengthen" question, would (C) have been suitable? I am just wondering how one should interpret "only some" in the LSAT. "Some" is an infamously ambiguous word, but does the "only" help to diminish some of that ambiguity (i.e. by suggesting that it is a small number)?

Thanks so much for your insights.

[ohthatpatrick]

(C) would strengthen, because it could counter the objection of "what if all the growth in population in the preserve just comes from other parts of the valley?", but it would not be a very likely correct answer because it would strengthen ever so mildly.

I think your intuition is right on point with how to interpret "only some".

It would mean some, but not all. There's no precise quantifier beyond that (it could still be above or below 50%), but the intended effect of "ONLY some" is to highlight that at least some of the increase in population in the preserve is just from other bears inside the valley.

[olaizola.mariana]

Got it, thank you!

[Aquamarine]

I can understand why E is an answer, but I still don't get why D is wrong.
I think D can weaken the argument too.
If the bear population in areas of the Abbimac Valley outside the Kiffer Forest Preserve has decreased, I think it can weaken the conclusion.
So Why can't D be an answer?

Please someone explain me.
Thanks in advance!

[contropositive]

I can understand why E is an answer, but I still don't get why D is wrong.
I think D can weaken the argument too.
If the bear population in areas of the Abbimac Valley outside the Kiffer Forest Preserve has decreased, I think it can weaken the conclusion.
So Why can't D be an answer?

Please someone explain me.
Thanks in advance!

D states that " the bears OUTSIDE the preserve have decreased" this would strengthen by suggesting that perhaps the decrease is due to the fact that their migrating to the preserve. In other words, their moving from outside to go to the preserve which is why the population has decreased outside the preserve, and the preserve population has increased.

E is a little subtle but as the instructors above and many others suggested, the conclusion is about the valley in general but we are only concerned about the preserve which is the northernmost part of the valley. E is saying well even if population in the preserve is increasing, the conclusion about the valley is wrong because the valley has remained the same.

[atzhang6v6]

I still do not understand why A is wrong...here is what I thought:
The conclusion says "the valley's bear pop will increase [if] the road is kept closed."
A suggests, I thought, it is not true because the increase is due to migration instead of the fact that the road is kept closed.
There is no correlation between the increasing and the fact tat the road is kept closed. (one does not lead to the other)
What makes A wrong?
Is it because A suggests the closing may actually lead to migration, and in that could support the conclusion because it would imply there was causation indirectly?

[seychelles1718]

Can one of the instructors please evaluate my explanation?

A) This doesn't specify what type of migration it is so we don't know the impact of this answer choice to the argument. Is it internal migration (moving from other parts of the Valley into the Preserve) or is it migration from outside of the Valley? Also, this answer choice only talks about why MOST of the increase took place. What about the other 49%? This answer choice is too vague to have any impact on the argument.

Unlike A, B and C specify the type of migration. However, because of the quantifier, "only some," which can be anywhere between 1% ~ 99%, the logical impact that B and C have on the argument is ambiguous. Both answer choices only tell us about the cause of SOME of the increase, so we don't know anything about the rest of the increase. If both B and C said ALL of the increase is due to such migration, the impact of both answer choices on the argument would be much more definite, as B would weaken while C would strengthen.

Although I wrote my own explanation above, I'd love to see any official explanation by manhattan instructors!

[ohthatpatrick]

Nice work! (The official explanation by an instructor is Noah's, at the top)

Essentially, the author is thinking that having the Preserve closed to car traffic is promoting higher birth/survival rates for bears, adding to the total of the overall Valley's bear population.

If we can find an answer that explains the uptick in the Preserve's bear population while NOT increasing the Valley's bear population, we will have weakened the argument.

(E) doesn't explain the uptick, but it tells us that the uptick in Preserve bears is NOT adding to the total of overall Valley's bear population, so we can infer that the uptick in Preserve bears is just a re-allocation of the Valley's overall population of bears.

If you have access to test 14, there's a similar type of thinking going on "is the uptick ADDING to the total overall number, or just redistributing the wealth?"
PT14, S2, Q10