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Alternate Cause - A weakener or not

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Re: Alternate Cause - A weakener or not [#permalink] New post 31 Jul 2013, 21:11
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miteshk wrote:
Chiranjeev,
This article helped me clear up a lot of confusion. But I still don't understand why are we being generous towards present/future tense in causality?
As you explained that with the present tense:
If 'Eating sugar leads to obesity',
Then 'Eating oil leads to obesity' doesn't weaken the previous statement because the author is not saying that only eating sugar leads to obesity.

Applying similar line of reasoning to following statements:
Eating sugar made Jon obese.
Eating oil made Jon obese.
Here also the author is not saying that only eating sugar made Jon obese. He could very well have meant that eating sugar was one of the reasons that made Jon obese.

Looking forward to your reply. Also I would appreciate if you remember any official examples displaying the above two concepts.


Hi Mitesh,

You have brought up a very interesting point here!

I was wondering when would someone ask this! :)

Let me ask you a question first.

What led to the economic growth of India in the first decade of this millennium?

Suppose you say, "Rising income of middle class".

Can I refute you by saying "No, it was just one of the factors. Rather, a combination of good governance and rising income of middle class led to the economic growth"?

Yes, I can say that because when I ask you "what led to economic growth", I am referring to entire growth and not a part of growth (which can be possibly explained by one of the two factors).

So, if anyone asks us, "what led to Y?". Either we say that X is one of the factors that led to Y or if we say that X led to Y, then it means that X alone led to Y.

Therefore, when we say X led to Y, any statement that indicates Z led to Y weakens our statement.

However, the case is very different for X leads to Y.

Suppose I ask you, what leads to good score on GMAT?
Suppose you say, hard work.

Now, can I refute your argument by saying, "Studying from good test prep company leads to good score". The answer is No here. I am not at all countering that hard work leads to good score. I am possibly presenting another way to achieve the same objective but not countering the original way.

Another analogy can be:

Statement "Road X leads to destination D" is not countered by a statement "Road Y leads to D".
On the other hand, Statement "Road X led Joe to destination D" is countered by a statement "Road Y led Joe to destination D".

Does it help?

Thanks,
Chiranjeev
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Re: Alternate Cause - A weakener or not [#permalink] New post 31 Jul 2013, 21:17
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Forgot to share official questions for X led to Y:

In the last decade there has been a significant decrease in coffee consumption. During this same time, there
has been increasing publicity about the adverse long-term effects on health of the caffeine in coffee.
Therefore, the decrease in coffee consumption must have been caused by consumers’ awareness of the
harmful effects of caffeine.
Which of the following, if true, most seriously calls into question the explanation above?
(A) On average, people consume 30 percent less coffee today than they did 10 years ago.
(B) Heavy coffee drinkers may have mild withdrawal symptoms, such as headaches, for a day or so after
significantly decreasing their coffee consumption.
(C) Sales of specialty types of coffee have held steady as sales of regular brands have declined.
(D) The consumption of fruit juices and caffeine-free herbal teas has increased over the past decade.
(E) Coffee prices increased steadily in the past decade because of unusually severe frosts in coffee-growing
nations.

Option E is the correct choice.


Which of the following most logically completes the argument given below?
People in isolated rain-forest communities tend to live on a largely vegetarian diet, and they eat little salt. Few of
them suffer from high blood pressure, and their blood pressure does not tend to increase with age, as is
common in industrialized countries. Such people often do develop high blood pressure when they move to cities
and adopt high-salt diets. Though suggestive, these facts do not establish salt as the culprit in high blood
pressure, however, because .
(A) genetic factors could account for the lack of increase of blood pressure with age among such people
(B) people eating high-salt diets and living from birth in cities in industrialized societies generally have a
tendency to have high blood pressure
(C) it is possible to have a low-salt diet while living in a city in an industrialized country
(D) there are changes in other aspects of diet when such people move to the city
(E) salt is a necessity for human life, and death can occur when the body loses too much salt

Option D is the correct choice.


Though sucking zinc lozenges has been promoted as treatment for the common cold, research has revealed no consistent effect. Recently, however, a zinc gel applied nasally has been shown to greatly reduce the duration of colds. Since the gel contains zinc in the same form and concentration as the lozenges, the greater the effectiveness of the gel must be due to the fact that cold virus tend to concentrate in the nose, not the mouth. Which of the following, if true, most seriously weakens the argument?
A. Experimental subjects who used the zinc gel not only had colds of shorter duration but also had less severe symptoms than did those who used a gel that did not contain zinc.
B. The mechanism by which zinc effects the viruses that caused the common cold has not been conclusively established.
C. To make them palatable, zinc lozenges generally contains other ingredients, such as citric acid,, that can interfere with the chemical activity of zinc.
D. No Zinc based remedy can have any effect unless it is taken or applied within 48 hrs of the onset of cold symptoms.
E. Drug company researchers experimenting with nasal spray based on zinc have found that it has much the same effect on colds as the gel does.

Option C is the correct choice.

In Morigia the average age of cars that are still in use has historically been seven years, but now it is nearly nine years. Car manufacturers claim that the current poor economy has forced people to put off buying new cars, and thus when the economy improves, the average age of cars will return to former levels. Which of the following, if true, most seriously calls into question the car manufacturers' prediction?
A. Fewer cars per year are now being manufactured in Morigia than were being manufactured there five years ago.
B. When the threat of job loss is particularly strong, people are reluctant to commit themselves to expensive purchases.
C. The older a car is, the greater the amount of upkeep it requires.
D. The air-pollution control devices now being used in cars manufactured in Morigia cost less than those that were used seven years ago.
E. Most people in Morigia now believe that replacing an old car with a new one has very undesirable ecological consequences.

Option E is the correct choice.

Thanks,
Chiranjeev
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Re: Alternate Cause - A weakener or not [#permalink] New post 01 Aug 2013, 04:13
egmat wrote:
Let me ask you a question first.

What led to the economic growth of India in the first decade of this millennium?

Suppose you say, "Rising income of middle class".

Can I refute you by saying "No, it was just one of the factors. Rather, a combination of good governance and rising income of middle class led to the economic growth"?

Yes, I can say that because when I ask you "what led to economic growth", I am referring to entire growth and not a part of growth (which can be possibly explained by one of the two factors).

So, if anyone asks us, "what led to Y?". Either we say that X is one of the factors that led to Y or if we say that X led to Y, then it means that X alone led to Y.

Therefore, when we say X led to Y, any statement that indicates Z led to Y weakens our statement.

However, the case is very different for X leads to Y.

Suppose I ask you, what leads to good score on GMAT?
Suppose you say, hard work.

Now, can I refute your argument by saying, "Studying from good test prep company leads to good score". The answer is No here. I am not at all countering that hard work leads to good score. I am possibly presenting another way to achieve the same objective but not countering the original way.


Chiranjeev,
Thanks for taking time to reply. Also appreciate the official examples which you provided for "X led to Y" concept.
1) But it seems you are reinforcing the same point with different examples. I am not worried about how to apply the concept. I am just thinking why is this so ? Should I just memorize this like a grammar rule?

2) Also I tried searching for official examples that displays "X leads to Y" concept.
The CR Question number 33 of Verbal Official Guide (2nd edition) (about Renaissance oil paintings) displays this concept but treats the alternate cause as a weakener.
Conclusion: Gesso causes deterioration
Although the question is about a strengthener, but it rejects option B stating that it shows an alternate cause & hence is a weakener.
Please correct me if I am wrong.
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Re: Alternate Cause - A weakener or not [#permalink] New post 04 Aug 2013, 17:59
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miteshk wrote:
1) But it seems you are reinforcing the same point with different examples. I am not worried about how to apply the concept. I am just thinking why is this so ? Should I just memorize this like a grammar rule?


Hi Mitesh,

The point of using different examples here and explaining them using leading questions was to explain the "why" part. I think you need to keep away your preconceived notions aside for 5 minutes while you read that post; probably, you'll be able to grasp it much better.

If the post still doesn't help, then search for other material on the web to help yourself. You should avoid at all costs remembering CR stuff like grammar rules.
miteshk wrote:
2) Also I tried searching for official examples that displays "X leads to Y" concept.
The CR Question number 33 of Verbal Official Guide (2nd edition) (about Renaissance oil paintings) displays this concept but treats the alternate cause as a weakener.
Conclusion: Gesso causes deterioration
Although the question is about a strengthener, but it rejects option B stating that it shows an alternate cause & hence is a weakener.
Please correct me if I am wrong.


Here's the question:
Art restorers who have been studying the factors that cause Renaissance oil paintings to deteriorate physically when subject to climatic changes have found that the oil paint used in these paintings actually adjusts to these changes well. The restorers therefore hypothesize that it is a layer of material called gesso, which is under the paint, that causes the deterioration.

Which of the following, if true , most strongly supports the restorers' hypothesis?

A.Renaissance oil paintings with a thin layer of gesso are less likely to show deterioration in response to climatic changes than those with a thicker layer.

B.Renaissance oil paintings are often painted on wooden panels, which swell when humidity increases and contract when it declines.

C.Oil paint expands and contracts readily in response to changes in temperature, but it absorbs little water and so is little affected by changes in humidity.

D.An especially hard and nonabsorbent type of gesso was the raw material for moldings on the frames of Renaissance oil paintings.

E.Gesso layers applied by Renaissance painters typically consisted of a coarse base layer onto which several increasingly fine-grained layers were applied.

Think what is happening in the passage. Is the passage trying to "explain" the deterioration of paintings? Is it trying to find out what led to deterioration or is it after something else?

Thanks,
Chiranjeev
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Re: Alternate Cause - A weakener or not [#permalink] New post 05 Aug 2013, 10:33
egmat wrote:
Here's the question:
Art restorers who have been studying the factors that cause Renaissance oil paintings to deteriorate physically when subject to climatic changes have found that the oil paint used in these paintings actually adjusts to these changes well. The restorers therefore hypothesize that it is a layer of material called gesso, which is under the paint, that causes the deterioration.

Which of the following, if true , most strongly supports the restorers' hypothesis?

A.Renaissance oil paintings with a thin layer of gesso are less likely to show deterioration in response to climatic changes than those with a thicker layer.

B.Renaissance oil paintings are often painted on wooden panels, which swell when humidity increases and contract when it declines.

C.Oil paint expands and contracts readily in response to changes in temperature, but it absorbs little water and so is little affected by changes in humidity.

D.An especially hard and nonabsorbent type of gesso was the raw material for moldings on the frames of Renaissance oil paintings.

E.Gesso layers applied by Renaissance painters typically consisted of a coarse base layer onto which several increasingly fine-grained layers were applied.

Think what is happening in the passage. Is the passage trying to "explain" the deterioration of paintings? Is it trying to find out what led to deterioration or is it after something else?

Thanks,
Chiranjeev


Chiranjeev,

As per my understanding, the passage is indeed trying to find out what led to deterioration. Here is what I think the passage is about :

Premise: Renaissance oil paintings deteriorate physically when subjected to climate changes.
Experts are looking over the factors which cause the deterioration.
Oil paint adjusts to climate changes => Oil Paint is not the cause.
Conclusion by the Art Experts: Gesso causes the deterioration.

This looks like a "X causes Y" kind of causality.
I am only concerned with choice B.
Choice B implies that an alternate cause-the wooden panels- could lead to the deterioration and hence the choice weakens the argument. This is even stated in the official explanation.
But this is contrary to the 1st takeaway of the article.
egmat wrote:
TAKE AWAYS

1. “X leads/can lead/will lead to Y” allows the possibility of an alternate route, Z, to reach the effect, Y. Therefore, an option statement presenting an alternate route does not weaken this conclusion type.


Please let me know what is wrong with my interpretation. :?
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Re: Alternate Cause - A weakener or not [#permalink] New post 06 Aug 2013, 19:18
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miteshk wrote:
egmat wrote:
Here's the question:
Art restorers who have been studying the factors that cause Renaissance oil paintings to deteriorate physically when subject to climatic changes have found that the oil paint used in these paintings actually adjusts to these changes well. The restorers therefore hypothesize that it is a layer of material called gesso, which is under the paint, that causes the deterioration.

Which of the following, if true , most strongly supports the restorers' hypothesis?

A.Renaissance oil paintings with a thin layer of gesso are less likely to show deterioration in response to climatic changes than those with a thicker layer.

B.Renaissance oil paintings are often painted on wooden panels, which swell when humidity increases and contract when it declines.

C.Oil paint expands and contracts readily in response to changes in temperature, but it absorbs little water and so is little affected by changes in humidity.

D.An especially hard and nonabsorbent type of gesso was the raw material for moldings on the frames of Renaissance oil paintings.

E.Gesso layers applied by Renaissance painters typically consisted of a coarse base layer onto which several increasingly fine-grained layers were applied.

Think what is happening in the passage. Is the passage trying to "explain" the deterioration of paintings? Is it trying to find out what led to deterioration or is it after something else?

Thanks,
Chiranjeev


Chiranjeev,

As per my understanding, the passage is indeed trying to find out what led to deterioration. Here is what I think the passage is about :

Premise: Renaissance oil paintings deteriorate physically when subjected to climate changes.
Experts are looking over the factors which cause the deterioration.
Oil paint adjusts to climate changes => Oil Paint is not the cause.
Conclusion by the Art Experts: Gesso causes the deterioration.

This looks like a "X causes Y" kind of causality.
I am only concerned with choice B.
Choice B implies that an alternate cause-the wooden panels- could lead to the deterioration and hence the choice weakens the argument. This is even stated in the official explanation.
But this is contrary to the 1st takeaway of the article.
egmat wrote:
TAKE AWAYS

1. “X leads/can lead/will lead to Y” allows the possibility of an alternate route, Z, to reach the effect, Y. Therefore, an option statement presenting an alternate route does not weaken this conclusion type.


Please let me know what is wrong with my interpretation. :?


Hi Mitesh,

I understand your concern. Option B is indeed a weakener in this passage. Actually, a very similar doubt has been asked by 12bhang on this thread. I would suggest that you read my response to him. The direct link to my post is:

alternate-cause-a-weakener-or-not-155034.html#p1251835

Let me know if you are still not clear.

Thanks,
Chiranjeev
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Re: Alternate Cause - A weakener or not [#permalink] New post 06 Aug 2013, 22:31
egmat wrote:

Hi Mitesh,

I understand your concern. Option B is indeed a weakener in this passage. Actually, a very similar doubt has been asked by 12bhang on this thread. I would suggest that you read my response to him. The direct link to my post is:

alternate-cause-a-weakener-or-not-155034.html#p1251835

Let me know if you are still not clear.

Thanks,
Chiranjeev


Chiranjeev,
Your discussion with 12bhang about marital relationships pointed out that Alternate cause was still not a weakener in that case. While in this case it is considered a weakener.
Still unclear :(
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Re: Alternate Cause - A weakener or not [#permalink] New post 07 Aug 2013, 23:21
Awesome :)
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Re: Alternate Cause - A weakener or not [#permalink] New post 09 Aug 2013, 19:23
Expert's post
miteshk wrote:
egmat wrote:

Hi Mitesh,

I understand your concern. Option B is indeed a weakener in this passage. Actually, a very similar doubt has been asked by 12bhang on this thread. I would suggest that you read my response to him. The direct link to my post is:

alternate-cause-a-weakener-or-not-155034.html#p1251835

Let me know if you are still not clear.

Thanks,
Chiranjeev


Chiranjeev,
Your discussion with 12bhang about marital relationships pointed out that Alternate cause was still not a weakener in that case. While in this case it is considered a weakener.
Still unclear :(


Hi Mitesh,

I understand your concern. Frankly, where we are heading is a very nuanced understanding of causal arguments (basically, causality in assumptions vs causality in conclusion) and I can't think of a shortcut to explain it to you. I'll need to write a full length article on it to give any satisfactory response to your query. Any less than that will not clear all doubts.

However, these days are running quite busy for me but sooner than later, I will bring up an article on this thing and will surely intimate you once I do that.

Thanks,
Chiranjeev
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Re: Alternate Cause - A weakener or not [#permalink] New post 10 Aug 2013, 21:59
2. A study of marital relationships in which one partner's sleeping and waking cycles differ from those of other partner reveals that such couples share fewer activities with each other and have more violent arguments than do couples in a relationship in which both partners follow the same sleeping and waking patterns . Thus, mismatched sleeping and waking cycles can seriously jeopardize a marriage.

Which of the following, if true, most seriously weakens the argument above?

Married couples in which both spouses follow the same sleeping and waking patterns also have arguments that can jeopardize the couple's marriage.

------------------------------------------------------------------------------
Hi,

Firstly the passage is not saying that the partners who follow the same sleeping and waking partners NEVER indulge in arguments that can jeopardize marriage. So it cant be a right answer
Secondly, how come something that happens outside a group under study be an ALTERNATE CAUSE for high occurrence of the same activity seen inside the group(partners with similar sleeping and waking patterns)?

Can you please explain?
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Re: Alternate Cause - A weakener or not [#permalink] New post 11 Aug 2013, 21:45
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Gsam2013 wrote:
2. A study of marital relationships in which one partner's sleeping and waking cycles differ from those of other partner reveals that such couples share fewer activities with each other and have more violent arguments than do couples in a relationship in which both partners follow the same sleeping and waking patterns . Thus, mismatched sleeping and waking cycles can seriously jeopardize a marriage.

Which of the following, if true, most seriously weakens the argument above?

Married couples in which both spouses follow the same sleeping and waking patterns also have arguments that can jeopardize the couple's marriage.

------------------------------------------------------------------------------
Hi,

Firstly the passage is not saying that the partners who follow the same sleeping and waking partners NEVER indulge in arguments that can jeopardize marriage. So it cant be a right answer
Secondly, how come something that happens outside a group under study be an ALTERNATE CAUSE for high occurrence of the same activity seen inside the group(partners with similar sleeping and waking patterns)?

Can you please explain?


Hi,

You are correct. Option A can be rejected on either of the two grounds mentioned by you.

Thanks,
Chiranjeev
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Re: Almost all of us would have heard of causal arguments and [#permalink] New post 28 Aug 2013, 00:40
egmat wrote:
Hi Skamal7 and Vikas,


In terms of X and Y, the conclusion says that X will lead to Y (X: removal of tariffs, Y: urban unemployment).Option E weakens this by indicating that by not doing anything (i.e. with the status quo of high tariffs), we'll have more urban employment. This indicates that X will probably lead to reduction in Y, than increase in Y.
(Here, Y is not an event which will happen or not happen. It is a continuous figure which may increase or decrease).



Hi Chiranjeev,

I think it should be "we will have more urban unemployment".

Thanks.
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Re: Alternate Cause - A weakener or not [#permalink] New post 03 Oct 2013, 17:50
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I think this official question may also add value to this thread. It is from GMAT Paper Tests.

Let's see how many get this right :)

Dutch elm disease, which is caused by the fungus C. ulmi spread by adult scolytid beetles, has already destroyed 70 percent of the elms in Greenwood Forest. Another naturally occurring fungus, P. oblonga, kills larvae of the scolytid beetle. Forest rangers plan to introduce P. oblonga into Greenwood Forest in order to save the remaining mature elms.

Which of the following, if true, would cast the most serious doubt on the plan’s prospects for success?

(A) During the last year, the scolytid beetle population in Greenwood Forest has decreased by 30 percent because of cold-weather conditions.
(B) Dutch elm disease cannot be abated by introducing chemical compounds used to arrest the diseases of many other species of tree.
(C) Introduction of P. oblonga saved elm trees in neighboring Gatemar and Lavemont forests.
(D) For P. oblonga to control scolytid beetles successfully, it must be established in a forest prior to the beetle infestation.
(E) Greenwood Forest has lost many maple trees because of a fungus infection.

-Chiranjeev
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Re: Alternate Cause - A weakener or not [#permalink] New post 03 Oct 2013, 20:54
egmat wrote:
I think this official question may also add value to this thread. It is from GMAT Paper Tests.

Let's see how many get this right :)

Dutch elm disease, which is caused by the fungus C. ulmi spread by adult scolytid beetles, has already destroyed 70 percent of the elms in Greenwood Forest. Another naturally occurring fungus, P. oblonga, kills larvae of the scolytid beetle. Forest rangers plan to introduce P. oblonga into Greenwood Forest in order to save the remaining mature elms.

Which of the following, if true, would cast the most serious doubt on the plan’s prospects for success?

(A) During the last year, the scolytid beetle population in Greenwood Forest has decreased by 30 percent because of cold-weather conditions.
(B) Dutch elm disease cannot be abated by introducing chemical compounds used to arrest the diseases of many other species of tree.
(C) Introduction of P. oblonga saved elm trees in neighboring Gatemar and Lavemont forests.
(D) For P. oblonga to control scolytid beetles successfully, it must be established in a forest prior to the beetle infestation.
(E) Greenwood Forest has lost many maple trees because of a fungus infection.

-Chiranjeev


Here is my take on it.

Analysis:
Dutch elm disease: cause by fungus C. Ulmi residing in adult Scolytid beetles.
Naturally occurring fungus, P. Oblonga, can stop the infestation of Scolytid beetles and hence save elm trees.

Question stem:
What weakens the plan?

Prethinking:
If some how introduction of new fungus, P. Oblonga, harms the trees differently there by reducing the count of elm, the plan would fail.
Or
If some how the introduction of the new fungus, P. Oblonga, does not make a difference or bring any considerable effect.

POE/ Answer analysis:
(A) During the last year, the scolytid beetle population in Greenwood Forest has decreased by 30 percent because of cold-weather conditions.
- This does not relate to Fungus, P. Oblonga and its effect.
(B) Dutch elm disease cannot be abated by introducing chemical compounds used to arrest the diseases of many other species of tree.
Again irrelevant. Does not correlate to the plans of Forest Rangers.
(C) Introduction of P. oblonga saved elm trees in neighboring Gatemar and Lavemont forests.
Does not weaken the plan. Infact gives kinda a credibility to Ranger's thought processes.
(D) For P. oblonga to control scolytid beetles successfully, it must be established in a forest prior to the beetle infestation.
This is it. This weakens the plan. Forest Rangers should have introduced fungus, P. Oblonga, way earlier. Nothing can be done, now. Plan might not work.
(E) Greenwood Forest has lost many maple trees because of a fungus infection.
Again irrelevant.


Chiranjeev: What do you think? :)
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Re: Alternate Cause - A weakener or not [#permalink] New post 04 Oct 2013, 09:39
Expert's post
vabhs192003 wrote:
egmat wrote:
I think this official question may also add value to this thread. It is from GMAT Paper Tests.

Let's see how many get this right :)

Dutch elm disease, which is caused by the fungus C. ulmi spread by adult scolytid beetles, has already destroyed 70 percent of the elms in Greenwood Forest. Another naturally occurring fungus, P. oblonga, kills larvae of the scolytid beetle. Forest rangers plan to introduce P. oblonga into Greenwood Forest in order to save the remaining mature elms.

Which of the following, if true, would cast the most serious doubt on the plan’s prospects for success?

(A) During the last year, the scolytid beetle population in Greenwood Forest has decreased by 30 percent because of cold-weather conditions.
(B) Dutch elm disease cannot be abated by introducing chemical compounds used to arrest the diseases of many other species of tree.
(C) Introduction of P. oblonga saved elm trees in neighboring Gatemar and Lavemont forests.
(D) For P. oblonga to control scolytid beetles successfully, it must be established in a forest prior to the beetle infestation.
(E) Greenwood Forest has lost many maple trees because of a fungus infection.

-Chiranjeev


Here is my take on it.

Analysis:
Dutch elm disease: cause by fungus C. Ulmi residing in adult Scolytid beetles.
Naturally occurring fungus, P. Oblonga, can stop the infestation of Scolytid beetles and hence save elm trees.

Question stem:
What weakens the plan?

Prethinking:
If some how introduction of new fungus, P. Oblonga, harms the trees differently there by reducing the count of elm, the plan would fail.
Or
If some how the introduction of the new fungus, P. Oblonga, does not make a difference or bring any considerable effect.

POE/ Answer analysis:
(A) During the last year, the scolytid beetle population in Greenwood Forest has decreased by 30 percent because of cold-weather conditions.
- This does not relate to Fungus, P. Oblonga and its effect.
(B) Dutch elm disease cannot be abated by introducing chemical compounds used to arrest the diseases of many other species of tree.
Again irrelevant. Does not correlate to the plans of Forest Rangers.
(C) Introduction of P. oblonga saved elm trees in neighboring Gatemar and Lavemont forests.
Does not weaken the plan. Infact gives kinda a credibility to Ranger's thought processes.
(D) For P. oblonga to control scolytid beetles successfully, it must be established in a forest prior to the beetle infestation.
This is it. This weakens the plan. Forest Rangers should have introduced fungus, P. Oblonga, way earlier. Nothing can be done, now. Plan might not work.
(E) Greenwood Forest has lost many maple trees because of a fungus infection.
Again irrelevant.


Chiranjeev: What do you think? :)


Very good job at the analysis. :) Even though I am tempted to tell the correct answer, I think I'll wait for a couple of more responses :)

-Chiranjeev
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Re: Alternate Cause - A weakener or not [#permalink] New post 06 Oct 2013, 18:42
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vabhs192003 wrote:
egmat wrote:
I think this official question may also add value to this thread. It is from GMAT Paper Tests.

Let's see how many get this right :)

Dutch elm disease, which is caused by the fungus C. ulmi spread by adult scolytid beetles, has already destroyed 70 percent of the elms in Greenwood Forest. Another naturally occurring fungus, P. oblonga, kills larvae of the scolytid beetle. Forest rangers plan to introduce P. oblonga into Greenwood Forest in order to save the remaining mature elms.

Which of the following, if true, would cast the most serious doubt on the plan’s prospects for success?

(A) During the last year, the scolytid beetle population in Greenwood Forest has decreased by 30 percent because of cold-weather conditions.
(B) Dutch elm disease cannot be abated by introducing chemical compounds used to arrest the diseases of many other species of tree.
(C) Introduction of P. oblonga saved elm trees in neighboring Gatemar and Lavemont forests.
(D) For P. oblonga to control scolytid beetles successfully, it must be established in a forest prior to the beetle infestation.
(E) Greenwood Forest has lost many maple trees because of a fungus infection.

-Chiranjeev


Here is my take on it.

Analysis:
Dutch elm disease: cause by fungus C. Ulmi residing in adult Scolytid beetles.
Naturally occurring fungus, P. Oblonga, can stop the infestation of Scolytid beetles and hence save elm trees.

Question stem:
What weakens the plan?

Prethinking:
If some how introduction of new fungus, P. Oblonga, harms the trees differently there by reducing the count of elm, the plan would fail.
Or
If some how the introduction of the new fungus, P. Oblonga, does not make a difference or bring any considerable effect.

POE/ Answer analysis:
(A) During the last year, the scolytid beetle population in Greenwood Forest has decreased by 30 percent because of cold-weather conditions.
- This does not relate to Fungus, P. Oblonga and its effect.
(B) Dutch elm disease cannot be abated by introducing chemical compounds used to arrest the diseases of many other species of tree.
Again irrelevant. Does not correlate to the plans of Forest Rangers.
(C) Introduction of P. oblonga saved elm trees in neighboring Gatemar and Lavemont forests.
Does not weaken the plan. Infact gives kinda a credibility to Ranger's thought processes.
(D) For P. oblonga to control scolytid beetles successfully, it must be established in a forest prior to the beetle infestation.
This is it. This weakens the plan. Forest Rangers should have introduced fungus, P. Oblonga, way earlier. Nothing can be done, now. Plan might not work.
(E) Greenwood Forest has lost many maple trees because of a fungus infection.
Again irrelevant.


Chiranjeev: What do you think? :)


You are absolutely correct. The correct option is D. Good job :)

Thanks,
Chiranjeev
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Re: Alternate Cause - A weakener or not [#permalink] New post 06 Oct 2013, 21:09
egmat wrote:
vabhs192003 wrote:
egmat wrote:
I think this official question may also add value to this thread. It is from GMAT Paper Tests.

Let's see how many get this right :)

Dutch elm disease, which is caused by the fungus C. ulmi spread by adult scolytid beetles, has already destroyed 70 percent of the elms in Greenwood Forest. Another naturally occurring fungus, P. oblonga, kills larvae of the scolytid beetle. Forest rangers plan to introduce P. oblonga into Greenwood Forest in order to save the remaining mature elms.

Which of the following, if true, would cast the most serious doubt on the plan’s prospects for success?

(A) During the last year, the scolytid beetle population in Greenwood Forest has decreased by 30 percent because of cold-weather conditions.
(B) Dutch elm disease cannot be abated by introducing chemical compounds used to arrest the diseases of many other species of tree.
(C) Introduction of P. oblonga saved elm trees in neighboring Gatemar and Lavemont forests.
(D) For P. oblonga to control scolytid beetles successfully, it must be established in a forest prior to the beetle infestation.
(E) Greenwood Forest has lost many maple trees because of a fungus infection.

-Chiranjeev


Here is my take on it.

Analysis:
Dutch elm disease: cause by fungus C. Ulmi residing in adult Scolytid beetles.
Naturally occurring fungus, P. Oblonga, can stop the infestation of Scolytid beetles and hence save elm trees.

Question stem:
What weakens the plan?

Prethinking:
If some how introduction of new fungus, P. Oblonga, harms the trees differently there by reducing the count of elm, the plan would fail.
Or
If some how the introduction of the new fungus, P. Oblonga, does not make a difference or bring any considerable effect.

POE/ Answer analysis:
(A) During the last year, the scolytid beetle population in Greenwood Forest has decreased by 30 percent because of cold-weather conditions.
- This does not relate to Fungus, P. Oblonga and its effect.
(B) Dutch elm disease cannot be abated by introducing chemical compounds used to arrest the diseases of many other species of tree.
Again irrelevant. Does not correlate to the plans of Forest Rangers.
(C) Introduction of P. oblonga saved elm trees in neighboring Gatemar and Lavemont forests.
Does not weaken the plan. Infact gives kinda a credibility to Ranger's thought processes.
(D) For P. oblonga to control scolytid beetles successfully, it must be established in a forest prior to the beetle infestation.
This is it. This weakens the plan. Forest Rangers should have introduced fungus, P. Oblonga, way earlier. Nothing can be done, now. Plan might not work.
(E) Greenwood Forest has lost many maple trees because of a fungus infection.
Again irrelevant.


Chiranjeev: What do you think? :)


You are absolutely correct. The correct option is D. Good job :)

Thanks,
Chiranjeev


Waiting for a new challenge...Chiranjeev, when is the next one coming? :)

-Vaibhav
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Re: Alternate Cause - A weakener or not [#permalink] New post 13 Oct 2013, 21:42
I was doing OG13 questions when I got confused with OG13 Q25 & 37(both weaken questions). After reading this article, all my doubts vanished & I was able to answer & understand those questions quickly. :-D
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Re: Alternate Cause - A weakener or not [#permalink] New post 16 Oct 2013, 02:51
Found this article incredibly helpful and decided to catch the next alternate cause beauty i found. Lo and behold for all you CR-soon-to-be-champs. This is an official GMAT prep question that I found quite interesting. The question itself is quite straightforward, but I thought that I'd add it to this thread to help everyone strengthen this concept. Thanks e-gmat. Great tip!

In the late 1980’s, the population of sea otters in the North Pacific Ocean began to
decline. Of the two plausible explanations for the decline—increased predation by killer
whales or disease—disease is the more likely. After all, a concurrent sharp decline in
the populations of seals and sea lions was almost certainly caused by a pollutionrelated
disease, which could have spread to sea otters, whereas the population of killer
whales did not change noticeably

Which of the following, if true, most seriously weakens the reasoning?

A. Killer whales in the North Pacific usually prey on seals and sea lions but will,
when this food source is scarce, seek out other prey.

B. There is no indication that substantial numbers of sea otters migrated to other
locations from the North Pacific in the 1980’s.

C. Along the Pacific coast of North America in the 1980’s, sea otters were absent
from many locations where they had been relatively common in former times.

D. Following the decline in the population of the sea otters, there was an increase
in the population of sea urchins, which are sea otters’ main food source.

E. The North Pacific populations of seals and sea lions cover a wider geographic
area than does the population of sea otters

As usual, please provide reasoning for why each option is correct / incorrect.

Cheers!
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Re: Alternate Cause - A weakener or not [#permalink] New post 16 Oct 2013, 06:43
Expert's post
egmat wrote:
miteshk wrote:
1) But it seems you are reinforcing the same point with different examples. I am not worried about how to apply the concept. I am just thinking why is this so ? Should I just memorize this like a grammar rule?


Hi Mitesh,

The point of using different examples here and explaining them using leading questions was to explain the "why" part. I think you need to keep away your preconceived notions aside for 5 minutes while you read that post; probably, you'll be able to grasp it much better.

If the post still doesn't help, then search for other material on the web to help yourself. You should avoid at all costs remembering CR stuff like grammar rules.
miteshk wrote:
2) Also I tried searching for official examples that displays "X leads to Y" concept.
The CR Question number 33 of Verbal Official Guide (2nd edition) (about Renaissance oil paintings) displays this concept but treats the alternate cause as a weakener.
Conclusion: Gesso causes deterioration
Although the question is about a strengthener, but it rejects option B stating that it shows an alternate cause & hence is a weakener.
Please correct me if I am wrong.


Here's the question:
Art restorers who have been studying the factors that cause Renaissance oil paintings to deteriorate physically when subject to climatic changes have found that the oil paint used in these paintings actually adjusts to these changes well. The restorers therefore hypothesize that it is a layer of material called gesso, which is under the paint, that causes the deterioration.

Which of the following, if true , most strongly supports the restorers' hypothesis?

A.Renaissance oil paintings with a thin layer of gesso are less likely to show deterioration in response to climatic changes than those with a thicker layer.

B.Renaissance oil paintings are often painted on wooden panels, which swell when humidity increases and contract when it declines.

C.Oil paint expands and contracts readily in response to changes in temperature, but it absorbs little water and so is little affected by changes in humidity.

D.An especially hard and nonabsorbent type of gesso was the raw material for moldings on the frames of Renaissance oil paintings.

E.Gesso layers applied by Renaissance painters typically consisted of a coarse base layer onto which several increasingly fine-grained layers were applied.

Think what is happening in the passage. Is the passage trying to "explain" the deterioration of paintings? Is it trying to find out what led to deterioration or is it after something else?

Thanks,
Chiranjeev



Friends,

This particular question is also discussed under this thread art-restorers-who-have-been-studying-161733.html#p1279149
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Re: Alternate Cause - A weakener or not   [#permalink] 16 Oct 2013, 06:43
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