gmat prep 1

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gmat prep 1

by jainrahul1985 » Tue Aug 16, 2011 6:10 am
Tiger beetles are such fast runners that they can capture virtually any nonflying insect. However, when running toward an insect, the beetles intermittently stop, and then, a moment later, resume their attack. Perhaps they cannot maintain their pace and must pause for a moment's rest; but an alternative hypothesis is that while running tiger beetles are unable to process the resulting rapidly changing visual information, and so quickly go blind and stop.

Which of the following, if discovered in experiments using artificially moved prey insects, would support one of the two hypotheses and undermine the other?

(A) When a prey insect is moved directly toward a beetle that has been chasing it, the beetle immediately turns and runs away without its usual intermittent stopping.
(B) In pursuing a moving insect, the beetles usually respond immediately to changes in the insect's direction, and pause equally frequently whether the chase is up or down an incline.
(C) The beetles maintain a fixed time interval between pauses, although when an insect that had been stationary begins to flee, the beetle increases its speed after its next pause.
(D) If, when a beetle pauses, it has not gained on the insect it is pursuing, the beetle generally ends its pursuit.
(E) When an obstacle is suddenly introduced just in front of running beetles, the beetles sometimes stop immediately, but they never respond by running around the barrier.

OA C . Experts please suggest why B is wrong
Source: — Critical Reasoning |

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by SticklorForDetails » Tue Aug 16, 2011 10:48 am
The problem with (B) is that it actually goes against either of the two hypotheses. The two arguments in question are:

1) The beetle stops because it's tired
2) The beetle stops because it can't process visual information while running

The first part of (B) would seem to argue against hypothesis #2, but the second part of (B) seems to argue against hypothesis #1, because if it's tiredness then it would stand to reason they would stop more often when going uphill. This (B) doesn't really support one of the two hypotheses.
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by GmatKiss » Tue Aug 16, 2011 12:16 pm
SticklorForDetails wrote:The problem with (B) is that it actually goes against either of the two hypotheses. The two arguments in question are:

1) The beetle stops because it's tired
2) The beetle stops because it can't process visual information while running

The first part of (B) would seem to argue against hypothesis #2, but the second part of (B) seems to argue against hypothesis #1, because if it's tiredness then it would stand to reason they would stop more often when going uphill. This (B) doesn't really support one of the two hypotheses.
thanks a lot :) i had the same query shooted by Rahul!

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by jainrahul1985 » Tue Aug 16, 2011 10:36 pm
This makes me understand why B is wrong but still confused why C is correct . The wording of C is puzzling me . Please explain .
SticklorForDetails wrote:The problem with (B) is that it actually goes against either of the two hypotheses. The two arguments in question are:

1) The beetle stops because it's tired
2) The beetle stops because it can't process visual information while running

The first part of (B) would seem to argue against hypothesis #2, but the second part of (B) seems to argue against hypothesis #1, because if it's tiredness then it would stand to reason they would stop more often when going uphill. This (B) doesn't really support one of the two hypotheses.

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by VivianKerr » Wed Aug 17, 2011 8:38 am
Conclusion 1 (Hypothesis 1): Beetles can't maintain pace.

Evidence: Beetles stop when running toward an insect, then resume.

Assumption: They don't stop for any other reason.

Conclusion 2 (Hypothesis 2): Beetles can't process visual info while running; they go blind + stop.

Evidence: Beetles stop when running toward an insect, then resume.

Assumptions: Their visual info is necessary to capturing an insect. Stopping will make them see again.

Question Rephrase: What data would STRENGTHEN 1 hypothesis & undermine the other.

Prediction: To strengthen 1, anything that shows they don't stop for any other reason & shows that their visual info is NOT necessary/stopping does not let them "see" again.

To strengthen 2, anything that shows their visual info is needed & that stopping will help, and also shows that they DON'T stop to rest.

C - With a fixed interval time, the beetle is probably NOT stopping b/c it's tired, esp. since it's increasing it's speed. Since it starts running again when the insect changes direction, it's likely because the beetle can "see" the insect.
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by voodoo_child » Thu Aug 18, 2011 4:58 am
Guys,
Correct answer is B) - Og12 Diagnostic 25

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by voodoo_child » Thu Aug 18, 2011 5:01 am
pls ignore. i got confused with b and c. The OA is C)

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by e-GMAT » Thu Aug 18, 2011 10:15 am
I would like to dispute the OA, The correct OA in my opinion is choice B. Choice C is not the correct answer. Please refer to OG 11/12 Question 25, page 83 if you need to see the official explanation. Read below if you need a more human readable explanation.

What is the question asking?
The question is asking you to select an answer choice that will weaken one hypothesis while strengthening the other. Remember, a single experiment must do this.

What is an irrefutable fact?
When running toward an insect, the beetles intermittently stop, and then, a moment later, resume their attack. - This is a fact that must be explained by the correct answer.

How does choice B achieve this?
Choice B states that while pursuing an insect that changes course abruptly (swerving), the beetle stops to alters the course. The frequency of stopping increases as the chase goes on because higher the number of times the insect changes course, greater is visual information that the beetle has to process. Note that this automatically dismisses hypothesis A because it explains an alternate cause for the Beetle stopping.

Why is choice C incorrect?
You could say that this experiment disproves either hypothesis. This choice states 2 things:
1. The beetle is able to change direction with the insect, implying that the beetle does not have a problem with changing direction. (note that you will have to ensure that this change is direction qualifies as "rapidly changing")
2. The number of pauses that a beetle takes is independent of whether he is going uphill or downhill, implying that beetle is not stopping because its tired but for some other reason. This is because if the beetle were to stop because of tiredness, he would stop more frequently while going uphill.
Hence, this choice in most probability weakens both hypotheses.

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by voodoo_child » Thu Aug 18, 2011 11:02 am
e-GMAT wrote:I would like to dispute the OA, The correct OA in my opinion is choice B. Choice C is not the correct answer. Please refer to OG 11/12 Question 25, page 83 if you need to see the official explanation. Read below if you need a more human readable explanation.

What is the question asking?
The question is asking you to select an answer choice that will weaken one hypothesis while strengthening the other. Remember, a single experiment must do this.

What is an irrefutable fact?
When running toward an insect, the beetles intermittently stop, and then, a moment later, resume their attack. - This is a fact that must be explained by the correct answer.

How does choice B achieve this?
Choice B states that while pursuing an insect that changes course abruptly (swerving), the beetle stops to alters the course. The frequency of stopping increases as the chase goes on because higher the number of times the insect changes course, greater is visual information that the beetle has to process. Note that this automatically dismisses hypothesis A because it explains an alternate cause for the Beetle stopping.

Why is choice C incorrect?
You could say that this experiment disproves either hypothesis. This choice states 2 things:
1. The beetle is able to change direction with the insect, implying that the beetle does not have a problem with changing direction. (note that you will have to ensure that this change is direction qualifies as "rapidly changing")
2. The number of pauses that a beetle takes is independent of whether he is going uphill or downhill, implying that beetle is not stopping because its tired but for some other reason. This is because if the beetle were to stop because of tiredness, he would stop more frequently while going uphill.
Hence, this choice in most probability weakens both hypotheses.
eGMAT - GMATPrep has flipped B and C. That's where even I got confused.

OG's B is GMATPrep's C
OG's C is GMATPrep's B