Critical Reasoning

RBBmba@2014 wrote:

DavidG@VeritasPrep wrote:

For A: If the other species on which deer tick larvae feed are found -- or NOT FOUND -- ONLY in areas also inhabited by white footed mice, then in BOTH the cases it's LIKELY that the ticks will feed on these other UNINFECTED species. Therefore, this option seems to STRENGTHEN the ARGUMENT in either case and subsequently doesn't really help us to EVALUATE the ARGUMENT.

A is irrelevant. Imagine the ticks also feed on squirrels. The plan would be to increase the number of squirrels in an area inhabited by white-footed mice, with the hope that many of the tics would feed on the squirrels rather than the mice, and so never contract the disease. Why would it matter whether squirrels were in areas without the mice? The disease wouldn't be there! We only care about the areas with disease-carrying mice.

Hi Dave,
While I can understand your point, I'd like to clarify what I intended to mean here -

Option A could be interpreted in the following ways as well, I guess.

First, If the other species on which deer tick larvae feed are found ONLY in areas also inhabited by white footed mice, then it's LIKELY that the ticks will feed on these other UNINFECTED species. Therefore, this option seems to STRENGTHEN the ARGUMENT.

Second, If the other species on which deer tick larvae feed are found NOT ONLY (now this could mean, in the mice affected areas + other areas) in areas also inhabited by white footed mice, then ALSO, irrespective of areas, it's LIKELY that the ticks will feed on these other UNINFECTED species and thus OVERALL infected ticks will likely decline. Therefore, this option seems to STRENGTHEN the ARGUMENT as well.

Hence, I concluded that Option A is unable to EVALUATE the ARGUMENT because in BOTH the cases -- with "NOT" and without "NOT" -- Option A seems to STRENGTHEN the ARGUMENT. But to be an OA of an EVALUATE CR, the option should STRENGTHEN the ARGUMENT in one hand (say,without "NOT") and WEAKEN the ARGUMENT in other hand (say, with "NOT").

Am I able to make myself clear ? Does this interpretation work ?

Let me know please!

I see what you're saying, but my sense is that this interpretation suffers from a couple of shortcomings. First there's a logical problem. If I have a plan, and you ask, "But will X happen?" to have a better understanding of whether the plan will work, it can't be true that a YES and a NO answer will both make the plan more likely succeed. (Though it could be the case that the question is irrelevant, and the plan would succeed in either case.) Think about it mathematically. My initial estimation for the probability of a plan working is 80%. You ask "will X happen?" Imagine that if the answer is YES, the probability becomes 90% that the plan will work. And that if the answer is NO, the probability becomes 90% that the plan will work. How can that be? Shouldn't my initial estimation have been 90% rather than 80%?

The second problem comes from this assumption: If the other species on which deer tick larvae feed are found ONLY in areas also inhabited by white footed mice[/color], then it's LIKELY that the ticks will feed on these other UNINFECTED species. [/i]

I don't think we can assume this. We already know from the prompt that tic larvae will feed on these new uninfected species. The question is whether, in areas inhabited by white-footed mice, the number of infected tics will go down if we introduce more of these new uninfected species. So the operative question is really, "what happens to the population size of the tics after we introduce more of the uninfected species?" If 10% of the tics switch from biting mice to biting uninfected hosts, but the population size of the tics doubles, you're going to end up with a greater overall number of infected tics. An answer to the question about whether the uninfected species exist in other areas can't tell us anything about what happens to the population size of tics in infected areas.

Hi Dave,
I don't think I got you this time properly

However, would be curious to know your thoughts on the same LYME DISEASE ARGUMENT in another Official CR: gmatprep-deer-ticks-and-lyme-disease. (The QUESTION STEM is DIFFERENT in this thread)

Could you please share your feedback for that one ?

P.S: I think, actually there are THREE DIFFERENT types of questions available from GMAC for this LYME DISEASE ARGUMENT.

RBBmba@2014 wrote:Hi Dave,
I don't think I got you this time properly

However, would be curious to know your thoughts on the same LYME DISEASE ARGUMENT in another Official CR: gmatprep-deer-ticks-and-lyme-disease. (The QUESTION STEM is DIFFERENT in this thread)

Could you please share your feedback for that one ?

P.S: I think, actually there are THREE DIFFERENT types of questions available from GMAC for this LYME DISEASE ARGUMENT.

Yep, it's a popular prompt - I just chimed in for other one as well. The easiest way to think of this one: imagine a radically simplified world in which there are two tics, X and Y. We expect the following to happen: X bites a mouse and gets infected. Y bites a squirrel and does not get infected. We want to decrease the odds of X getting infected, so we introduce a second squirrel. If X and Y both bite squirrels, and no new tics appear, we have an infection-free zone. We want to know if this will be the likely outcome. (The plan could fail for a variety of reasons: maybe introducing more tic food causes an explosion in the tic population and some of these new tics bite the mouse and get infected. Maybe the tics feed multiple times and introducing another food source increases the odds that X will survive long enough to bite a mouse, etc.)

An answer to the question of whether there are squirrels in other mouse-free locations does not tell us what will happen in the area we care about.

DavidG@VeritasPrep wrote:The easiest way to think of this one: imagine a radically simplified world in which there are two tics, X and Y. We expect the following to happen: X bites a mouse and gets infected. Y bites a squirrel and does not get infected. We want to decrease the odds of X getting infected, so we introduce a second squirrel. If X and Y both bite squirrels, and no new tics appear, we have an infection-free zone. We want to know if this will be the likely outcome. (The plan could fail for a variety of reasons: maybe introducing more tic food causes an explosion in the tic population and some of these new tics bite the mouse and get infected. Maybe the tics feed multiple times and introducing another food source increases the odds that X will survive long enough to bite a mouse, etc.)

An answer to the question of whether there are squirrels in other mouse-free locations does not tell us what will happen in the area we care about.

So, can we say that it boils down to this -- irrespective of areas where squirrels are found (be it mouse-free locations or mouse-inhabited locations) the Option A seems to STRENGTHEN the ARGUMENT, and thus doesn't actually help to EVALUATE the ARGUMENT.

Did I get this correct ?

Hey Dave,
Any thoughts on this Sir ?

Curious to hear from you. Much thanks in advance!

So, can we say that it boils down to this -- irrespective of areas where squirrels are found (be it mouse-free locations or mouse-inhabited locations) the Option A seems to STRENGTHEN the ARGUMENT, and thus doesn't actually help to EVALUATE the ARGUMENT.

Did I get this correct ?

If an affirmative answer to the question posed in A really did strengthen the argument in a material way, it would be useful information. A is wrong because it sheds no light on whether the proposed plan will work. Put another way, imagine that you'd just carried out the plan and set a bunch of squirrels free in a disease-infested area. If you were to get an email later that day telling you that sometimes the squirrels also existed in areas that didn't have the white-footed mice, you wouldn't have sense of whether your plan was working.

GMATGuruNY wrote: If the deer tick population is limited because there are too few ANIMALS for the deer tick to feed on, then all that matters is that the deer ticks LACK FOOD.
No TYPE of animal is specified because this information is irrelevant.
If more food is provided -- whether in the form of OTHER SPECIES or INFECTED WHITE-FOOTED MICE -- the hungry deer ticks are likely to feed on this food.
Thus, if the additional food comes in the form of OTHER SPECIES, the deer ticks are likely to feed on these other species, strengthening the conclusion that there will be a decline in the number of ticks acquiring lyme disease from infected white-footed mice.

Hi GMATGuruNY,
After going through your above analysis and the other one https://www.beatthegmat.com/the-deer-th ... 86068.html on the same answer choice, I'm getting confused as it appears to me these two comments are contradictory because for the same rephrase you've mentioned in this thread it STRENGTHENS the CONCLUSION and in other thread that I referred to you've mentioned that it WEAKENS the CONCLUSION!

Could you please help ?

RBBmba@2014 wrote:

GMATGuruNY wrote: If the deer tick population is limited because there are too few ANIMALS for the deer tick to feed on, then all that matters is that the deer ticks LACK FOOD.
No TYPE of animal is specified because this information is irrelevant.
If more food is provided -- whether in the form of OTHER SPECIES or INFECTED WHITE-FOOTED MICE -- the hungry deer ticks are likely to feed on this food.
Thus, if the additional food comes in the form of OTHER SPECIES, the deer ticks are likely to feed on these other species, strengthening the conclusion that there will be a decline in the number of ticks acquiring lyme disease from infected white-footed mice.

Hi GMATGuruNY,
After going through your above analysis and the other one https://www.beatthegmat.com/the-deer-th ... 86068.html on the same answer choice, I'm getting confused as it appears to me these two comments are contradictory because for the same rephrase you've mentioned in this thread it STRENGTHENS the CONCLUSION and in other thread that I referred to you've mentioned that it WEAKENS the CONCLUSION!

Could you please help ?

In my post above, B has been rephrased as follows:
The size of the deer tick population is NOT currently limited by the availability of animals for the tick's larval stage to feed on.
This rephrase STRENGTHENS the conclusion.
In the other post, B has been rephrased in the opposite direction:
The size of the deer tick population IS currently limited by the availability of animals for the tick's larval stage to feed on.
This rephrase -- since it is the opposite of the first rephrase -- WEAKENS the conclusion.

GMATGuruNY wrote:In my post above, B has been rephrased as follows:
The size of the deer tick population is NOT currently limited by the availability of animals for the tick's larval stage to feed on.
This rephrase STRENGTHENS the conclusion.
In the other post, B has been rephrased in the opposite direction:
The size of the deer tick population IS currently limited by the availability of animals for the tick's larval stage to feed on.
This rephrase -- since it is the opposite of the first rephrase -- WEAKENS the conclusion.

I can understand this but I got confused from your 2nd post in the first page of this thread. It's as follows:

GMATGuruNY wrote:If the deer tick population is limited because there are too few ANIMALS for the deer tick to feed on, then all that matters is that the deer ticks LACK FOOD.
If more food is provided -- whether in the form of OTHER SPECIES or INFECTED WHITE-FOOTED MICE -- the hungry deer ticks are likely to feed on this food.
Thus, if the additional food comes in the form of OTHER SPECIES, the deer ticks are likely to feed on these other species, strengthening the conclusion that there will be a decline in the number of ticks acquiring lyme disease from infected white-footed mice.

You see the RED parts - they seem to be contradictory to what you've mentioned in your IMMEDIATE last post. Isn't it ?

RBBmba@2014 wrote:your 2nd post in the first page of this thread. It's as follows:

GMATGuruNY wrote:If the deer tick population is limited because there are too few ANIMALS for the deer tick to feed on, then all that matters is that the deer ticks LACK FOOD.

You see the RED parts - they seem to be contradictory to what you've mentioned in your IMMEDIATE last post. Isn't it ?

Good catch.
To allay confusion, I've removed the red portion from my second post.

GMATGuruNY wrote:
This CR links an increase in the AMOUNT OF UNINFECTED FOOD to a decrease in the NUMBER OF INFECTED TICKS.

We are being asked to EVALUATE this link.
Thus, the correct answer must either STRENGTHEN or WEAKEN this link: it must show why INCREASING THE AMOUNT OF UNINFECTED FOOD will -- or will not -- lead to a DECREASE IN THE NUMBER OF INFECTED TICKS.

To understand the answer choices more easily, rephrase them without the word whether.

(E) Whether the other species on which deer tick larvae feed harbor any other bacteria that ticks transmit to humans.
Outside the scope. The argument isn't about other bacteria.
Eliminate E.

Dear Mitch,
If I rephrase the choice E:
the other species on which deer tick larvae feed harbor any a lot of other bacteria that ticks transmit to humans
In choice E, does not that WEAKEN the argument that 'the number of ticks acquiring the bacterium would likely decline.'? Although there are 'other Bactria', the conclusion itself contains word 'bacterium' which is general word any nay Bactria.

Can you please help?

Thanks

Mo2men wrote:Dear Mitch,
If I rephrase the choice E:
the other species on which deer tick larvae feed harbor any a lot of other bacteria that ticks transmit to humans
In choice E, does not that WEAKEN the argument that 'the number of ticks acquiring the bacterium would likely decline.'? Although there are 'other Bactria', the conclusion itself contains word 'bacterium' which is general word any nay Bactria.

Can you please help?

Thanks

E, rephrased as a basic statement:
The other species on which deer tick larvae feed harbor other bacteria that ticks transmit to humans.
The conclusion is constrained to the number of ticks infected with the bacterium that causes LYME DISEASE.
Information about other bacteria is irrelevant because it tells us nothing about the number of ticks that will be infected with the bacterium that causes lyme disease.
Eliminate E.