#24 - The Kiffer Forest Preserve, in the northernmost part

[Administrator]

Complete Question Explanation

Weaken—#%. The correct answer choice is (E)

Like many questions that deal with numbers and percentages, this one can be tricky if we don’t have
a strong grasp on the information provided. The premises are as follows: The Kiffer Forest Preserve
is the portion of the Abbimac Valley most populated with bears. During the past eight years, the main
road through the preserve has been closed, and the bear population in the preserve has doubled.

Based on the premises listed above, the author concludes that if the road remains closed, the bear
population of the whole valley will increase. As with many of the LSAT’s number/percentage stimuli,
this one provides limited information; we know that the bear population in the preserve (which is,
after all, only a portion of the Valley) has doubled over the past eight years, perhaps based on the
road closing, but we have no information about what’s been happening around the rest of the Valley.
If the overall, Valley-wide bear population has been increasing, then the author’s argument becomes
stronger.

If the overall population has not also seen an increase over the past eight years, the author’s
conclusion is then provided significantly less support. We should keep this in mind, since the
question stem requires us to find the answer that weakens the argument.

Answer choice (A): Regardless of whether the changes in the preserve’s bear population were
attributable to migration, this choice fails to weaken the author’s argument, which regards the bear
population of the whole valley.

Answer choice (B): This answer choice provides very limited information. If “some” were from
other areas within the valley, this means “at least one” bear had migrated from elsewhere. This
choice does not weaken the argument from the stimulus.

Answer choice (C): This answer choice is limited in the same way as incorrect answer choice (B)
above. The information that “some” of the bears migrated from outside the valley does not weaken
the author’s argument, which is that an increase in the valley’s bear population is to be expected
based on the increases in the preserve’s bear population.

Answer choice (D): This choice provides us with another vague piece of information, of limited
usefulness. Perhaps the bear population in other areas has decreased by one over the past 8 years.
Without more information about the increase in the preserve and in the valley overall, this choice
does not weaken the argument in the stimulus and thus cannot be the correct answer choice.

Answer choice (E): This is the correct answer choice. If the overall Valley population of bears
has not increased, the author’s argument is seriously undermined. The conclusion that the Valley’s
bear population will increase is based on the increased population in the preserve. If the overall
population has not increased, this means that the bears that arrived in the preserve had come from
nearby, within the very same valley. If this is the case, there is far less reason to believe the author’s
conclusion, so this must be the correct answer to this weaken question.

[Nina]

How can answer E undermines the argument?
and why is answer A incorrect?


Many thanks!

[Justin Eleff]

(E) undermines the argument because it exploits the gap in the question's argument, which is that because the population in the PRESERVE has increased, the population in the VALLEY must have increased, too -- so if the road continues to be closed, the population in the VALLEY will increase further. But (E) tells us that the overall population in the valley hasn't increased; instead, it appears that we're simply seeing that more and more of the valley's bears have moved into the preserve (which covers part of the valley only). Maybe the bear population in the PRESERVE will continue to increase, but if keeping the road closed has not had any effect on the VALLEY's population so far, why would it going forward?

(A) does directly remove keeping the road closed as the reason why MOST of the preserve's bear population has increased, but because it leaves open the possibility that SOME increase in the bear population of the preserve (and perhaps of the larger valley) can be attributed to keeping the road closed, it doesn't destroy the argument quite as thoroughly as (E) does.

[Nina]

Thank you, Justin! It makes so much sense to me right now!

[netherlands]

Hi there PS,

This question gave me a hard time. I totally thought I had I'd gotten it right when I answered it! Can you help me understand?

So the preserve in the forest (which is part of the Valley) has experienced an increase since the road has been closed. So the VALLEY will (continue?) to increase as long as the road is kept closed. ( I missed the preserve vs valley detail at first, which is prob a big part of what led to my getting it wrong).

So in order for the total valley to be increasing I have to assume that growth is due to bears outside the valley or "new" bears in some way entering the preserve. In order to weaken the idea that the valley population will increase I have to find an answer showing that the increase in the preserve population or whatever future increase does not consist of "new" bears that weren't already in the valley.

A) the increase was due to migration: it doesnt say whether it was internal or external migration so it doesn't weaken or strengthen the argument's claim.

B) only some of the migration was internal - in which case I'm assuming that the majority of any migration was external? that would strengthen the argument. correct?

C) only some of the migration was external - could that not weaken the claim that the valley population will increase if the majority of migration was assumedly internal and we're assuming it will continue to be that way? But even though there was not a lot of external migration doesn't preclude the possibility that there was a ton of cub births, correct?

D) the population in the valley has decreased while the preserve increased- what do I pull from this? should I assume that this indicates the growth from the preserve was internal in which it could weaken the claim that the valley will grow. But at time same time- can't the population have decreased due to something like deaths while the preserve bears are having more cubs in which case the claim that valley will increase could take place? Basically 20 non preserve valley bears die - but 75 are born in the preserve and another 75 enter via external migration.

E) the population in the valley has remained the same over the 8 years- I think my first thought was that this was a contradiction of what the stimulus said and was automatically wrong. But the stimulus said that the PRESERVE increased not necessarily that the valley did.I guess the point in this one is that if there was an increase in the preserve but not in the valley then no "new" bears were ever introduced so there's no reason to believe that they ever will be or that the valley popl will increase.

Any further or additional insight would be appreciated!

[David Boyle]

Hi there PS,

This question gave me a hard time. I totally thought I had I'd gotten it right when I answered it! Can you help me understand?

So the preserve in the forest (which is part of the Valley) has experienced an increase since the road has been closed. So the VALLEY will (continue?) to increase as long as the road is kept closed. ( I missed the preserve vs valley detail at first, which is prob a big part of what led to my getting it wrong).

So in order for the total valley to be increasing I have to assume that growth is due to bears outside the valley or "new" bears in some way entering the preserve. In order to weaken the idea that the valley population will increase I have to find an answer showing that the increase in the preserve population or whatever future increase does not consist of "new" bears that weren't already in the valley.

A) the increase was due to migration: it doesnt say whether it was internal or external migration so it doesn't weaken or strengthen the argument's claim.

B) only some of the migration was internal - in which case I'm assuming that the majority of any migration was external? that would strengthen the argument. correct?

C) only some of the migration was external - could that not weaken the claim that the valley population will increase if the majority of migration was assumedly internal and we're assuming it will continue to be that way? But even though there was not a lot of external migration doesn't preclude the possibility that there was a ton of cub births, correct?

D) the population in the valley has decreased while the preserve increased- what do I pull from this? should I assume that this indicates the growth from the preserve was internal in which it could weaken the claim that the valley will grow. But at time same time- can't the population have decreased due to something like deaths while the preserve bears are having more cubs in which case the claim that valley will increase could take place? Basically 20 non preserve valley bears die - but 75 are born in the preserve and another 75 enter via external migration.

E) the population in the valley has remained the same over the 8 years- I think my first thought was that this was a contradiction of what the stimulus said and was automatically wrong. But the stimulus said that the PRESERVE increased not necessarily that the valley did.I guess the point in this one is that if there was an increase in the preserve but not in the valley then no "new" bears were ever introduced so there's no reason to believe that they ever will be or that the valley popl will increase.

Any further or additional insight would be appreciated!

Hello netherlands,

In short, you're right that the preserve and the valley are different. The closed road roped in some bears to the preserve, maybe, so maybe they weren't able to go make baby bears with the bears in the valley outside the preserve. If the road's opened, maybe there'll be more little bears born outside the preserve, but fewer in the preserve. In any case, yes, there's no reason to believe that the whole valley's bear population'll rise if the road stays closed.
Let me think a little about your comments on the answer choices some more.

Hope that helps,
David

[David Boyle]

Hi there PS,

This question gave me a hard time. I totally thought I had I'd gotten it right when I answered it! Can you help me understand?

So the preserve in the forest (which is part of the Valley) has experienced an increase since the road has been closed. So the VALLEY will (continue?) to increase as long as the road is kept closed. ( I missed the preserve vs valley detail at first, which is prob a big part of what led to my getting it wrong).

So in order for the total valley to be increasing I have to assume that growth is due to bears outside the valley or "new" bears in some way entering the preserve. In order to weaken the idea that the valley population will increase I have to find an answer showing that the increase in the preserve population or whatever future increase does not consist of "new" bears that weren't already in the valley.

A) the increase was due to migration: it doesnt say whether it was internal or external migration so it doesn't weaken or strengthen the argument's claim.

B) only some of the migration was internal - in which case I'm assuming that the majority of any migration was external? that would strengthen the argument. correct?

C) only some of the migration was external - could that not weaken the claim that the valley population will increase if the majority of migration was assumedly internal and we're assuming it will continue to be that way? But even though there was not a lot of external migration doesn't preclude the possibility that there was a ton of cub births, correct?

D) the population in the valley has decreased while the preserve increased- what do I pull from this? should I assume that this indicates the growth from the preserve was internal in which it could weaken the claim that the valley will grow. But at time same time- can't the population have decreased due to something like deaths while the preserve bears are having more cubs in which case the claim that valley will increase could take place? Basically 20 non preserve valley bears die - but 75 are born in the preserve and another 75 enter via external migration.

E) the population in the valley has remained the same over the 8 years- I think my first thought was that this was a contradiction of what the stimulus said and was automatically wrong. But the stimulus said that the PRESERVE increased not necessarily that the valley did.I guess the point in this one is that if there was an increase in the preserve but not in the valley then no "new" bears were ever introduced so there's no reason to believe that they ever will be or that the valley popl will increase.

Any further or additional insight would be appreciated!

Hello netherlands,

In short, you're right that the preserve and the valley are different. The closed road roped in some bears to the preserve, maybe, so maybe they weren't able to go make baby bears with the bears in the valley outside the preserve. If the road's opened, maybe there'll be more little bears born outside the preserve, but fewer in the preserve. In any case, yes, there's no reason to believe that the whole valley's bear population'll rise if the road stays closed.
Let me think a little about your comments on the answer choices some more.

Hope that helps,
David

Hello netherlands,

Adding some more: well, the road may only have roped off part of the preserve, maybe--if it roped off any at all. And: I'm not sure this problem deserved all the careful thought you put into it, but I'm glad you worked so hard!
Anyway:

1) Answer E is the only one that discusses the whole valley's population, which is helpful.
2) I'm not sure if choices A through D have any definite message, but it's true that both B and C, maybe, could strengthen the argument a little, since if not all the preserve's bear population increase is from migration (from wherever), maybe some of it is natural increase (having babies) in the preserve, and maybe the road helps with that (road closure may keep the preserve sort of shut-off from outside so that the babies stay there, instead of wandering OUTSIDE the valley to another place?).
Hope that helps,

David

[Basia W]

Hello,

I have a question about the correct answer choice- which I nearly chose. However I know weaken choices are supposed to make the conclusion less likely to be true and follow from the premises but I didn't choose this answer because the stimulus states that the population has near doubled, whereas this answer states that it has stayed the same amount. In a weaken question can we actively disprove the premises as well?

Thank you,

best,

Basia

[David Boyle]

Hello,

I have a question about the correct answer choice- which I nearly chose. However I know weaken choices are supposed to make the conclusion less likely to be true and follow from the premises but I didn't choose this answer because the stimulus states that the population has near doubled, whereas this answer states that it has stayed the same amount. In a weaken question can we actively disprove the premises as well?

Thank you,

best,

Basia

Hello,

Usually the conclusion gets weakened, but once in a while, maybe something might help weaken the premises--or at least weaken the force of the premises. (I.e., if a premise is that the local ice cream store is closed on Sunday, then new information that a space ship lands on Sunday and brings ice cream, may make the local store's Sunday closure less relevant.)
Anyway, here, the point of E, in context, is that the bears in that particular preserve may not matter much, since their numbers have remained the same pretty much. So, the increase in bears may be in parts of the valley outside that preserve: thus, the closing of the road through the preserve may not really be important.

David

[sgd2114]

Hi,

After reading the above, I see why (E) is correct. However, I still have a hard time eliminating (D), which I chose when taking the exam. Any further explanation would be greatly appreciated. Thank you!