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# Boreal owls range over a much larger area than do other owls

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Re: Boreal owls range over a much larger area than do other owls [#permalink]
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Understanding the Passage

Boreal owls range over a much larger area than do other owls of similar size.

Boreal Owls >> Other Owls of similar size – in terms of size of area

The reason for this behavior is that the small mammals on which owls feed are especially scarce in the forests where boreal owls live, and the relative scarcity of prey requires the owls to range more extensively to find sufficient food.

The explanation for the fact given in the first statement is that
1. Food is scarce for Boreal owl i.e. less food per unit of area
2. Thus, more area required to get enough food to survive

While this could be an explanation for the larger range of Boreal owls, there could be other explanations too. For example, boreal owls are more aggressive than other owls and thus, by nature, keep a bigger area to themselves even when the food is not scarce.

Understanding the Question Stem

The question asks us to support the explanation. The 2nd statement is an explanation for the first statement.

In general, if X is given as an explanation for Y, we can strengthen the explanation by
1. suggesting that X is indeed an explanation for Y
a. by eliminating other explanations
b. by presenting an example in which the absence of X meant the absence of Y
2. suggesting that X indeed happened if the existence of X itself can be questioned. (In other words, if we are not even sure whether X has happened, we can strengthen “X is the explanation for Y” by indicating that X has happened. If we already know, as a fact, that X has happened, then we cannot strengthen the argument by indicating that X has happened.)

Please note that “X is an explantion for Y” can NEVER be strengthened by saying that Y indeed happened. You can think about it.

In this question, Y = “Boreal Owls >> Other Owls of similar size – in terms of size of range”

X = “Food is scarce for Boreal owl i.e. less food per unit of area. Thus, more area required to get enough food to survive”

Option Evaluation

(A)Some boreal owls range over an area eight times larger than the area over which any other owl of similar size ranges.
Incorrect- This option just supports the fact (Y), whose explanation is given. However, as stated above, “X is an explanation for Y” can NEVER be supported by supporting Y.

(B)Boreal owls range over larger areas in regions where food of the sort eaten by small mammals is sparse than they do in regions where such food is abundant
Correct- The fact that food eaten by small mammals is sparse indicates that small mammals are sparse in those regions. Think about it. If food for a species in a region is sparse, NOT many members of the species can exist in that region. Simply because there is not enough food.

Thus, this option means that boreal owls range over larger areas in regions where small mammals are sparse than they do in areas where small mammals are abundant.

Thus, this option indicates that the density of boreal owls in a region is dependent on the sparsity or density of their food in the region. Thereby, this option strengthens the explanation that the reason boreal owls range over larger areas than other owls is sparsity of their food.

(C)After their young hatch, boreal owls must hunt more often than before in order to feed both themselves and their newly hatched young.
Incorrect- This option presents a comparison between two stages of boreal owls: before their young hatch and after their young hatch. However, this option doesn’t suggest any reason why boreal owls range over larger areas than other owls.

(D)Sometimes individual boreal owls hunt near a single location for many weeks at a time and do not range farther than a few hundred yar
Incorrect- This option indicates that sometimes (which means at least once), individual boreal owls can find enough food in a small region.

Let’s make this option stronger by changing “sometimes” to “most of the times”

Most of the times, individual boreal owls hunt near a single location for many weeks at a time and do not range farther than a few hundred yards.

This variation casts a doubt on the fact that boreal owls range over larger areas than other owls. This variation has no impact on the explanation; this changed option casts doubt on whether Y didn’t happen. This can never impact the statement that X is an explanation for Y.

(E) The boreal owl requires less food, relative to its weight, than is required by members of other owl species.
Incorrect- This option can weaken the explanation rather than strengthen it. If boreal owls require less food, then they don’t need to range over larger areas because of sparsity of food. If they need less food, they can find that food in the same size of the areas as other owls do.

In this case, the sparsity of food may not be able to explain the larger range of boreal owls.
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Re: Boreal owls range over a much larger area than do other owls [#permalink]
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Hi guys,

IMO B

A. Some boreal owls range over an area eight times larger than the area over which any other owl of similar size ranges this answer does not add any support, just repeats the fact
B. Boreal owls range over larger areas in regions where food of the sort eaten by small mammals is sparse than they do in regions where such food is abundant. Hold
C. After their young hatch, boreal owls must hunt more often than before in order to feed both themselves and their newly hatched young the text talks about boreal owls in general
D. Sometimes individual boreal owls hunt near a single location for many weeks at a time and do not range rather than a few hundred yards. the text doesn't say anything about this
E. The boreal owl requires less food, relative to its weight, than is required by members of other owl species. nothing to do with the text

Could some post the OA?

What's the source?

Thanks
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Re: Boreal owls range over a much larger area than do other owls [#permalink]
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I picked (C) because.....

B. Boreal owls range over larger areas in regions where food of the sort eaten by small mammals is sparse than they do in regions where such food is abundant.

As per my understanding, (B) says opposite of what is given in the premise. Boreal owls range over larger areas where food eaten by small mammals is sparse. If food for small mammals is sparse then small mammals will not be found in those areas as they will gone to other places in search for their food.
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Re: Boreal owls range over a much larger area than do other owls [#permalink]
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premises : Boreal owls range over a much larger area than do other owls of similar size
The reason for this behavior is probably that the small mammals on which owls feed are especially scarce in the forests where boreal owls live.

the second premises clearly says it is the prey that is forcing owls to wander. on the other hand if the prey roamed in one target area the owls have no reason to leave

B supports this

B. Boreal owls range over larger areas in regions where food of the sort eaten by small mammals is sparse than they do in regions where such food is abundant.
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Re: Boreal owls range over a much larger area than do other owls [#permalink]
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The OA is B and it is coming from OG verbal question 59

But I really don't agree with this one.

First answer B is talking about "food eaten by the small mammals" not the small mamals themselves on which the owls prey. The explanation of the OG says that the presence of the small mammals and the food they eat is correlated and that abundance of this food means abundance of small mammals. But I don't think this inference is obvious as a perfectly valid explanation would be that the abundance of small mammals foods is due to the scarcity of their prey. And understood this way B weakens the explanation instead of strengthening it.

Second I think answer D is a way better choice. Indeed if D is correct then this means that when the boreal owl does not have to look for food and has a single location where to hunt, it does not range over a very large area as it usually does. Then, we can correctly infer that the reason the boreal owl range over a very large area is indeed because it needs to look for food, therefore D confirms the explanation.
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Re: Boreal owls range over a much larger area than do other owls [#permalink]
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Here I have two sentences.
Could anyone tell me whether the comparison in the two sentences is different?

(1) Boreal owls range over a much larger area than do other owls of similar size.
(2) Some boreal owls range over an area eight times larger than the area over which any other owl of similar size ranges.

I have been told that the second sentence is comparing different groups of boreal owls, while the first one is making a comparison between boreal owls and other owls.
Also, the OG solution has mentioned the same.

Is there any difference?? are they actually not the same?
Really confused.

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Re: Boreal owls range over a much larger area than do other owls [#permalink]
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Boreal owls range over a much larger area than do other owls of similar size. The reason for this behavior is that the small mammals on which owls feed are especially scarce in the forests where boreal owls live, and the relative scarcity of prey requires the owls to range more extensively to find sufficient food.

Which of the following ,if true, most helps to confirm the explanation above?

I also selected D as an option taking similar reasons as Darmody mentioned. But if the OG has an option B as correct answer so we will have to orient ourselves according to GMAT thinking to solve the Verbal problems and get a good score. Now the question stem suggests that the Boreal owls range a much larger area than other owls of similar size as the small mammals on which owl feed are scarce in the forests and hence they range in the larger area in search of food.

So, Final solution goes like this,

A. Some boreal owls range over an area eight times larger than the area over which any other owl of similar size ranges.
This is just a fact which doesn't confirm the explanation.

B. Boreal owls range over larger areas in regions where food of the sort eaten by small mammals is sparse than they do in regions where such food is abundant.
Since Boreal owls feed on mammals and these mammals food is sparse in certain area, So in these areas they roam around in a larger area to find food and hence Boreal owls have to range in a larger area to hunt these mammals. In the areas where food is abundant for these mammals, the mammals don't roam around for food and the Boreal owls has a similar trend of not roaming around for these mammals.
So , this might be a good confirmation to the explanation.

C. After their young hatch, boreal owls must hunt more often than before in order to feed both themselves and their newly hatched young.
This is natural and nowhere related to general tendency of Boreal owl's range being larger. Out of scope.

D. Sometimes individual boreal owls hunt near a single location for many weeks at a time and do not range rather than a few hundred yards.
This is talking about individual boreal owl and sometimes boreal owl do such thing which might be due to their ill health etc. So this option is very close but B is a better option.

E. The boreal owl requires less food, relative to its weight, than is required by members of other owl species.
Totally out of scope...
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Re: Boreal owls range over a much larger area than do other owls [#permalink]
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vnigam21 wrote:
Here I have two sentences.
Could anyone tell me whether the comparison in the two sentences is different?

(1) Boreal owls range over a much larger area than do other owls of similar size.
(2) Some boreal owls range over an area eight times larger than the area over which any other owl of similar size ranges.

I have been told that the second sentence is comparing different groups of boreal owls, while the first one is making a comparison between boreal owls and other owls.
Also, the OG solution has mentioned the same.

Is there any difference?? are they actually not the same?
Really confused.

Dear vnigam21,

I'm happy to respond.

There are a couple important differences in those two comparisons. Comparison #1 is very general, and by implication it discusses ALL boreal owls. Comparison #2 instead limits the scope to SOME boreal owls, not all, and it introduces a specific numerical measure for how much larger the area is. Those are the two most important differences between these comparisons.

Does this make sense?
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Re: Boreal owls range over a much larger area than do other owls [#permalink]
mikemcgarry wrote:
vnigam21 wrote:
Here I have two sentences.
Could anyone tell me whether the comparison in the two sentences is different?

(1) Boreal owls range over a much larger area than do other owls of similar size.
(2) Some boreal owls range over an area eight times larger than the area over which any other owl of similar size ranges.

I have been told that the second sentence is comparing different groups of boreal owls, while the first one is making a comparison between boreal owls and other owls.
Also, the OG solution has mentioned the same.

Is there any difference?? are they actually not the same?
Really confused.

Dear vnigam21,

I'm happy to respond.

There are a couple important differences in those two comparisons. Comparison #1 is very general, and by implication it discusses ALL boreal owls. Comparison #2 instead limits the scope to SOME boreal owls, not all, and it introduces a specific numerical measure for how much larger the area is. Those are the two most important differences between these comparisons.

Does this make sense?
Mike

Thanks for the reply mikemcgarry. Sorry, But my question is still unanswered. I got the differences that you mentioned above....

(1) Boreal owls range over a much larger area than do other owls of similar size.
I am clear with this statement, it is making a comparison between boreal owls and other owls of similar size.

But I am not clear with this 2nd statement's explanation as given in the OG,

(2) Some boreal owls range over an area eight times larger than the area over which any other owl (how come this any other owl is boreal owl??) of similar size ranges.
the second sentence is comparing different groups of boreal owls??? how?
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Re: Boreal owls range over a much larger area than do other owls [#permalink]
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Boreal owls range over a much larger area than do other owls of similar size. The reason for this behavior is that the small mammals on which owls feed are especially scarce in the forests where boreal owls live, and the relative scarcity of prey requires the owls to range more extensively to find sufficient food.

Which of the following ,if true, most helps to confirm the explanation above?

A. Some boreal owls range over an area eight times larger than the area over which any other owl of similar size ranges
Okay, some boreal owls might range over such a large area, but it doesn't talk about the entire boreal owl community. This is just a fact set.

B. Boreal owls range over larger areas in regions where food of the sort eaten by small mammals is sparse than they do in regions where such food is abundant.
Correct. If the small mammals on which these owls feed range over a large area, then definitely the owls will also have to range over a much larger area, since these small mammals are already scarce, making it even more difficult for the owls to feed on them.

C. After their young hatch, boreal owls must hunt more often than before in order to feed both themselves and their newly hatched young
Okay, let them take care of their family, but it doesn't say anything about the owls scattering over a large area.

D. Sometimes individual boreal owls hunt near a single location for many weeks at a time and do not range rather than a few hundred yards.
Okay, let them hunt in a single location. Out of context

E. The boreal owl requires less food, relative to its weight, than is required by members of other owl species.
Okay, let this owl require lesser quantity of food than other owls do. Out of context.
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Re: Boreal owls range over a much larger area than do other owls [#permalink]
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Boreal owls range over a much larger area than do other owls of similar size. The reason for this behavior is that the small mammals on which owls feed are especially scarce in the forests where boreal owls live, and the relative scarcity of prey requires the owls to range more extensively to find sufficient food.

KEY TO NOTE: BOREAL OWLS NEED TO RANGE OVER A LARGER AREA TO EAT. THIS IMPLIES THAT OWLS OF SIMILAR SIZES LIVE IN AREAS WHERE FOOD IS MORE ABUNDANT, SO SIMILAR OWLS DO NOT NEED TO RANGE OVER AS LARGE A AREA.

Which of the following, if true, most helps to confirm the explanation above? --> STRENGTHEN

A. Some boreal owls range over an area eight times larger than the area over which any other owl of similar size ranges
- Only new info that is added here is that the range of boreal owls is 8x larger than any other owl of similar size. Who cares if its 5x or 20x?

B. Boreal owls range over larger areas in regions where food of the sort eaten by small mammals is sparse than they do in regions where such food is abundant.
- Ah ha! You can find this in the notes above. Basically says Boreal owls NEED to range over larger areas where food is scarce...and if this were not the case (if boreal owls lived in areas where food was more abundant), they would range over a smaller area

C. After their young hatch, boreal owls must hunt more often than before in order to feed both themselves and their newly hatched young
- Isn't this the case with ALL owls who have hatchlings? (All GOOD owl parents catch food for their young)

D. Sometimes individual boreal owls hunt near a single location for many weeks at a time and do not range rather than a few hundred yards.
- That sucks, I know if I waited weeks to eat, I would get pretty grumpy...yes, I know this whole thing sounds ridiculous. So what? What is this adding to the argument? How does this strengthen their ability to find food in their environment?

E. The boreal owl requires less food, relative to its weight, than is required by members of other owl species.
- Who cares about the relative amount of food the boreal owl needs as compared to members of other owl species?

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Re: Boreal owls range over a much larger area than do other owls [#permalink]
Boreal owls range over a much larger area than do other owls of similar size. The reason for this behavior is that the small mammals on which owls feed are especially scarce in the forests where boreal owls live, and the relative scarcity of prey requires the owls to range more extensively to find sufficient food.

Which of the following ,if true, most helps to confirm the explanation above?

(A) Some boreal owls range over an area eight times larger than the area over which any other owl of similar size ranges.

(B) Boreal owls range over larger areas in regions where food of the sort eaten by small mammals is sparse than they do in regions where such food is abundant

(C) After their young hatch, boreal owls must hunt more often than before in order to feed both themselves and their newly hatched young.

(D) Sometimes individual boreal owls hunt near a single location for many weeks at a time and do not range farther than a few hundred yards.

(E) The boreal owl requires less food, relative to its weight, than is required by members of other owl species.

LakerFan24 wrote:
E. The boreal owl requires less food, relative to its weight, than is required by members of other owl species.
- Who cares about the relative amount of food the boreal owl needs as compared to members of other owl species?

Hi IanStewart avigutman AndrewN
IanStewart and avigutman AndrewN

I have no problem with the correct option (B), but I am a bit obsessed with the option (E). In previous posts in this thread, not many people have talked about this incorrect option, so I decided to write my post and hope you could share some thoughts when you have time.

We are given a statement as a general fact that boreal owls range over a much larger area than do other owls of similar size. Then we are asked to support an explanation that boreal owls need to range more extensively to find enough food than other types of owls, because owls' prey, small mammals, are scarce in boreal forests.

Quote:
(E) The boreal owl requires less food, relative to its weight, than is required by members of other owl species.

I know the negation technique only works for the assumption questions, but I could not help but negated it and found that the negated option is a strong weakener:

(E)' The boreal owl requires the same amount or higher amount of food, relative to its weight, than required by other owls.

If we focus on the "higher amount" part*, this could weaken the proposed explanation--it is not because of the scarcity of small mammals in the boreal forests that made boreal owls need to fly further to find enough food than other owls of similar size, but because of the boreal owls' greater needs for food. Hence, even if small mammals are as abundant in the boreal forests as in other regions, boreal owls still need fly further to hunt more food because they just need more food.

I am not to say that if an option, after negated, can weaken the argument, the option itself would be a strengthener. I feel that there is no such logic relationship even though I cannot articulate why (is it because the logic opposite of the concept "strengthen" is not just "weaken" but a combination of "no impact" and "weaken"?)

But looking at the original option (E), I feel that it gives some evidence to the proposed explanation--if the boreal owl has a smaller appetite than other owls of similar size, we can be more sure that boreal owls range over a larger area probably because of the scarcity of small mammals, instead of an alternative reason that boreal owls simply just need more food.

Compared with the option (B), the option (E) supports the proposed explanation in a more indirect way. And the information in (E) is not the information we would expect to be true if we accept the proposed explanation. I think that might be why the option (B) is better, as the information in (B) is something we would expect to be true. But still, I feel that the option (E) is a strengthener. I was surprised to find that official explanations say the option (E) tends to undermine the proposed explanation.

I feel that my logic is a bit tangled, could you help point out the mistakes I make in the above line of thing?

Thank you very much!!!

PS. I only focus on the "higher amount" part in the negated version of (E), because I am unsure what effect the statement "The boreal owl requires the same amount of food as other owls" would put on the proposed explanation. I feel that it is neutral or even a supporter, as it helps preempt an alternative explanation.

PS.I had difficulty tagging experts in my posts for some unclear technical reasons (the function of "mention this user" does not work), and sorry in advance if the tagging repeats.

Originally posted by GraceSCKao on 21 Apr 2022, 08:46.
Last edited by GraceSCKao on 26 Apr 2022, 02:14, edited 2 times in total.
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Re: Boreal owls range over a much larger area than do other owls [#permalink]
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GraceSCKao wrote:
Boreal owls range over a much larger area than do other owls of similar size. The reason for this behavior is that the small mammals on which owls feed are especially scarce in the forests where boreal owls live, and the relative scarcity of prey requires the owls to range more extensively to find sufficient food.

Which of the following ,if true, most helps to confirm the explanation above?

(A) Some boreal owls range over an area eight times larger than the area over which any other owl of similar size ranges.

(B) Boreal owls range over larger areas in regions where food of the sort eaten by small mammals is sparse than they do in regions where such food is abundant

(C) After their young hatch, boreal owls must hunt more often than before in order to feed both themselves and their newly hatched young.

(D) Sometimes individual boreal owls hunt near a single location for many weeks at a time and do not range farther than a few hundred yards.

(E) The boreal owl requires less food, relative to its weight, than is required by members of other owl species.

LakerFan24 wrote:
E. The boreal owl requires less food, relative to its weight, than is required by members of other owl species.
- Who cares about the relative amount of food the boreal owl needs as compared to members of other owl species?

Hi @IanStewart @avigutman @AndrewN
IanStewart and avigutman AndrewN

I have no problem with the correct option (B), but I am a bit obsessed with the option (E). In previous posts in this thread, not many people have talked about this incorrect option, so I decided to write my post and hope you could share some thoughts when you have time.

We are given a statement as a general fact that boreal owls range over a much larger area than do other owls of similar size. Then we are asked to support an explanation that boreal owls need to range more extensively to find enough food than other types of owls, because owls' prey, small mammals, are scarce in boreal forests.

(E) The boreal owl requires less food, relative to its weight, than is required by members of other owl species.

I know the negation technique only works for the assumption questions, but I could not help but negated it and found that the negated option is a strong weakener:

(E)' The boreal owl requires the same amount or higher amount of food, relative to its weight, than required by other owls.

If we focus on the "higher amount" part*, this could weaken the proposed explanation--it is not because of the scarcity of small mammals in the boreal forests that made boreal owls need to fly further to find enough food than other owls of similar size, but because of the boreal owls' greater needs for food. Hence, even if small mammals are as abundant in the boreal forests as in other regions, boreal owls still need fly further to hunt more food because they just need more food.

I am not to say that if an option, after negated, can weaken the argument, the option itself would be a strengthener. I feel that there is no such logic relationship (even though I cannot articulate why--is it because the logic opposite of the concept "strengthen" is not just "weaken" but a combination of "no impact" and "weaken"?)

But looking at the original option (E), I feel that it gives some evidence to the proposed explanation--if the boreal owl has a smaller appetite than other owls of similar size, we can be more sure that boreal owls range over a larger area probably because of the scarcity of small mammals, instead of an alternative reason that boreal owls simply just need more food.

Compared with the option (C), the option (E) supports the proposed explanation in a more indirect way. And the information in (E) is not the information we would expect to be true if we accept the proposed explanation. I think that is also why the option (C) is better, as the information in (C) is just something we would expect to be true. But still, I feel that the option (E) is a strengthener. I was surprised to find that official explanations say the option (E) tends to undermine the proposed explanation.

I feel that my logic is a bit tangled in this question, could you help point out the mistakes I make in the above line of thing?

Thank you very much!!!

PS. I only focus on the "higher amount" part since it is unclear to me how a statement "The boreal owl requires the same amount of food as other owls" would affect the proposed explanation. I feel that it is neutral or even a stronger, as that statement also helps preempt an alternative explanation.

PS.I had difficulty tagging experts in my posts for some unclear technical reasons (the function of "mention this user" does not work), and sorry in advance if the tagging repeats.

Hello, GraceSCKao. First off, I am not a big fan of the negation technique for any question, even assumption questions. This is not to say that negation cannot be put to effective use, just that I prefer to leave answer choices as they are when I assess them. If I were going to negate (E), I would do so in the following manner:

Quote:
(E) The boreal owl does not require less food, relative to its weight, than is required by members of other owl species.

That is it. Does not require less is not synonymous with what you wrote, requires the same amount or higher. You seem to have taken an associated thought "for a ride," as GMATNinja might say. Think about the following scenario:

• A fuel gauge in Car A reads "F" for "full" when the amount of fuel in the tank reaches 12 gallons
• A fuel gauge in Car B also reads "F" for "full" when the amount of fuel in its tank reaches 12 gallons

Now, I can reasonably assert that Car B does not require less fuel than does Car A for its fuel gauge to read "F," but I cannot in any way comment on the relative sizes of the two fuel tanks or fuel gauges beyond the 12-gallon figure. You have to stick strictly to the information given.

I am not going to tell you how you need to approach CR questions. Ask ten different Experts, and you will likely see a split between those who negate on assumption questions and those who do not, those who read the question stem first and those who do not, and so on. But I cannot think of a single one who would tell you to take your eye off the passage.

Perhaps answer choice (E) looks a little less appealing to you now. Thank you for thinking to ask. (By the way, the mention function has never worked for me, so I go about mentioning users in a much more roundabout way. I find a post in which someone has been mentioned, create a response to that post, copy the command in brackets, then abandon the post and paste the command in a new post that I want to write, changing the name of the recipient (twice).)

- Andrew
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Re: Boreal owls range over a much larger area than do other owls [#permalink]
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GraceSCKao wrote:
Looking at the original option (E), I feel that it gives some evidence to the proposed explanation--if the boreal owl has a smaller appetite than other owls of similar size, we can be more sure that boreal owls range over a larger area probably because of the scarcity of small mammals, instead of an alternative reason that boreal owls simply just need more food.

Hi GraceSCKao, I like what you did here. I agree that (E) eliminates a potential alternative explanation (which is indeed one of the common ways in which we bolster a proposed explanation in CR). I think the reason it's wrong has to do with the specific phrasing in the question stem: "help to confirm the explanation above."
This is different from the typical language that we see, along the lines of "most seriously calls into question the explanation above?" or "provides the strongest support for the explanation above?" (these are both taken from official GMAT problems).
Confirming an explanation and supporting an explanation are similar, but the subtle difference between them makes choice (E) not quite right.
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Re: Boreal owls range over a much larger area than do other owls [#permalink]
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GraceSCKao wrote:
I know the negation technique only works for the assumption questions, but I could not help but negated it and found that the negated option is a strong weakener:

(E)' The boreal owl requires the same amount or higher amount of food, relative to its weight, than required by other owls.

If we focus on the "higher amount" part*, this could weaken the proposed explanation--it is not because of the scarcity of small mammals in the boreal forests that made boreal owls need to fly further to find enough food than other owls of similar size, but because of the boreal owls' greater needs for food. Hence, even if small mammals are as abundant in the boreal forests as in other regions, boreal owls still need fly further to hunt more food because they just need more food.

My view of "the negation technique" is the same as AndrewN's. I never use it, because I'd rather think about what an answer says than about the opposite of what it says. And on this forum, I often see people make mistakes because they misapply a negation test. Correctly applied, it does work though, so if people find it useful, they should use it, and if an expert recommends it, I won't disagree with them too vehemently.

But let's insert a simplified version of E (first without negation) into a simplified version of the argument to see what effect it has:

Boreal owls need to fly far away to find food, because the food they need is hard to find. This makes sense, because boreal owls barely need to eat anything.

Now I think it's clear that answer E doesn't make sense. If the owl doesn't need to eat much, it shouldn't need to fly far to find food, even if food is scarce. So as written, E doesn't help to "confirm the explanation" provided. When you negate E, I don't think you're finding a 'weakener'; the more the owl needs to eat, the more flying around we'd expect it to do, so the negated E enhances the explanation, and the original version of E is a slight weakener, at least as I've rephrased it. As written, E is so cagey that it barely says anything -- "the boreal owl requires less food [how much less?], relative to its weight [how much does it weigh?] than" other owls. I'd be looking for a better answer on that basis alone.
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Re: Boreal owls range over a much larger area than do other owls [#permalink]
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AndrewN wrote:
First off, I am not a big fan of the negation technique for any question, even assumption questions. This is not to say that negation cannot be put to effective use, just that I prefer to leave answer choices as they are when I assess them. If I were going to negate (E), I would do so in the following manner:

Quote:
(E) The boreal owl does not require less food, relative to its weight, than is required by members of other owl species.

That is it.

• A fuel gauge in Car A reads "F" for "full" when the amount of fuel in the tank reaches 12 gallons
• A fuel gauge in Car B also reads "F" for "full" when the amount of fuel in its tank reaches 12 gallons

Now, I can reasonably assert that Car B does not require less fuel than does Car A for its fuel gauge to read "F," but I cannot in any way comment on the relative sizes of the two fuel tanks or fuel gauges beyond the 12-gallon figure. You have to stick strictly to the information given.
- Andrew

avigutman wrote:
GraceSCKao wrote:
But looking at the original option (E), I feel that it gives some evidence to the proposed explanation--if the boreal owl has a smaller appetite than other owls of similar size, we can be more sure that boreal owls range over a larger area probably because of the scarcity of small mammals, instead of an alternative reason that boreal owls simply just need more food.

Hi GraceSCKao, I like what you did here. I agree that (E) eliminates a potential alternative explanation (which is indeed one of the common ways in which we bolster a proposed explanation in CR). I think the reason it's wrong has to do with the specific phrasing in the question stem: "help to confirm the explanation above."
This is different from the typical language that we see, along the lines of "most seriously calls into question the explanation above?" or "provides the strongest support for the explanation above?" (these are both taken from official GMAT problems).
Confirming an explanation and supporting an explanation are similar, but the subtle difference between them makes choice (E) not quite right.

IanStewart wrote:
Let's insert a simplified version of E (first without negation) into a simplified version of the argument to see what effect it has:

Boreal owls need to fly far away to find food, because the food they need is hard to find. This makes sense, because boreal owls barely need to eat anything.

Now I think it's clear that answer E doesn't make sense. If the owl doesn't need to eat much, it shouldn't need to fly far to find food, even if food is scarce. So as written, E doesn't help to "confirm the explanation" provided. When you negate E, I don't think you're finding a 'weakener'; the more the owl needs to eat, the more flying around we'd expect it to do, so the negated E enhances the explanation, and the original version of E is a slight weakener, at least as I've rephrased it. As written, E is so cagey that it barely says anything -- "the boreal owl requires less food [how much less?], relative to its weight [how much does it weigh?] than" other owls. I'd be looking for a better answer on that basis alone.

Thank you so much AndrewN avigutman and IanStewart !
On days of reflection, I think I could see why the option (E) is not ideal now, thanks to your valuable insights from different angles.

I think the option (E) has two problems:

1. Even though I think the option (E) helps preempt an alternative explanation (the owls' appetite issue), supporting the proposed explanation in some way, it does not really help confirm the proposed explanation. As Avigutman points out in his post, providing support for an explanation is different from confirming the explanation. Initially I thought that I was dealing with a "strengthen" type CR question, so I felt the option (E) is not that bad. But I neglected the question's exact requirement. My takeaway from this experience is that while the classification of CR question types might still be helpful, I must focus on the exact requirement for every question.

2. The negation of the option (E) has a mixed message.

As AndrewN points out in his post, the negated option (E) is just "The boreal owl does not require less food, relative to its weight, than is required by members of other owl species." I think that this is equivalent to "the same amount to higher amount," but what is interesting is that the two parts have different impacts on the proposed explanation.

In my opinion, if the boreal owls need the same amount of food, relative to its weight, as other owls need, this information helps supporting the proposed explanation by eliminating an alternative explanation why boreal owls fly further. But if the boreal owls need higher amount of food, this information might cast some doubts on the proposed explanation by providing an alternative explanation. So, the negated option (E) is a strengthener and a weakener at the same time, paradoxically.

But I am also aware that IanStewart has interpreted the option (E) and its negation differently in his response and I could also understand his line of thinking: the more the owl needs to eat, the more flying around we'd expect it to do, so the negated E enhances the explanation, and the original version of E is a slight weakener, at least as I've rephrased it. As written, E is so cagey that it barely says anything -- "the boreal owl requires less food [how much less?].

I am not certain about the reason of the difference in the interpretations of the option (E). But I am certain that if the option (E) were a correct answer, it would deliver a more clear message. And more importantly, the original (E) does not help confirm the proposed explanation. My takeaway from this experience is that sometimes applying negation might not help reasoning at all.

I would like to thank the three experts once again for sharing their insights and thoughts on the option (E).
Thank you!
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Re: Boreal owls range over a much larger area than do other owls [#permalink]

Quote:
­Which of the following ,if true, most helps to confirm the explanation above?

So  far, I have seen question stems that ask about stengthening the conclusion. But in this case, the "explanation" thst the question stem is referring to seems to be the evidence given in the question prompt. Yet, the OA seems like it is strengthening the conclusion and not the evidence. What does "explanation" refer to, in this case?

Re: Boreal owls range over a much larger area than do other owls [#permalink]
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