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Citing the frequency with which gum disease and heart disease occur in

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Magoosh GMAT Instructor
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Re: Citing the frequency with which gum disease and heart disease occur in  [#permalink]

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New post 09 Oct 2013, 16:10
Reinfrank2011 wrote:
mikemcgarry wrote:
[
The conclusion of the prompt argument posits a causal relationship ----- "periodontal disease is a cause of a variety of cardiovascular problems" and we are asked to weaken the argument. Demonstrating "no cause" is precisely what we have to do, in order to weaken this argument. As I explained above, the logic of the argument is the classic correlation-implies-causality mistake. If P & Q are correlated, a very effective weakener for this the causation argument is to show that something else accounts for the correlation of P & Q. This is precisely what (B) does. It tells us (brushing & flossing regularly) are correlated with (exercise & healthy diet) --- one could say, they are both "caused" by a person's overall health-awareness & quality of self-care. Brushing & flossing cause the absences of periodontal disease: that's common knowledge. Regular exercise and a health diet cause the low frequency of heart disease: that's also common knowledge. Therefore, lack of brushing and flossing would lead to a higher frequency of periodontal disease, and lack of exercise & a poor diet would lead to a higher frequency of heart disease. That's precisely how these two could be correlated without having a causal relationship.


How does the logic used to justify the answer choice NOT commit the same error of judgement that the author or the original argument did, that correlation implies causation? All this says it that people do not have gum problems are more likely to not have cardiovascular problems. Even if you take it imply correlation, how does proof of correlation deny causation? EX: "Not being shot in the head is correlated with not dying, THEREFORE that fact weakens the argument that being shot in the head causes death?". Please explain.

Great question.
Again, we have
Premise: P is found with Q (P is correlated with Q)
Conclusion: P causes Q
Of course, the error is the unsubstantiated jump from correlation to causality.

The OA, (B), essentially says "the cause of P is correlated with the cause of Q"
First of all, we don't know why this would be true, but we don't have to --- we take premises and statements in answer choices as fait accompli, beyond question. So, suppose (B) is true, for whatever reason. What would be the logical consequences of (B)?
Notice, also: we don't repeat the mistake at a higher level --- there is absolutely no reason to move from statement (B) to the totally illogical statement "the cause of P causes the cause of Q". That would be disastrously illogical, but that's an absolutely unnecessary step, irrelevant to the argument involved with this choice.
Here's the logic --- if the cause of P is correlated with the cause of Q, this means, where one is found, we will tend to find the other. In the many situations in which the two are found together, then the cause of P will cause P, and, separately, the cause of Q will cause Q, and therefore P and Q will be found together. In other situations, in which both are absent, then the absence of this cause of P will make P less likely to occur, and the absence of this cause of Q will make Q less likely to occur, and thus we will have an elevated likelihood of scenarios in which the absence of P and the absence of Q concur. Thus, on both counts, this statement would create conditions in which P & Q are correlated, and this would be an alternate explanation ---- i.e. how P & Q could be correlated even though P has absolutely nothing to do with causing Q.

Does all this make sense?
Mike :-)
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Re: Citing the frequency with which gum disease and heart disease occur in  [#permalink]

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New post 28 Dec 2013, 09:07
Hi Semwal,

As others have pointed out E is actually a strengthener.

GMAT loves to do this sort of thing, put in lots of negatives to try and confuse you.

When this happens you need to be super logical, take a little more time and work through the sentence phrase by phrase. This way you work out what is the negative of what, and will give you a clear sense of the meaning.

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Re: Citing the frequency with which gum disease and heart disease occur in  [#permalink]

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New post 14 Feb 2014, 02:34
can anyone pls explain y B is OA.. it seems to strengthen the argument.
People who brush and floss their teeth regularly are also more likely to exercise and eat a healthy diet.
means NO periodontal disease ----->NO cardiovascular problems

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Re: Citing the frequency with which gum disease and heart disease occur in  [#permalink]

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New post 21 Jul 2015, 06:15
Citing the frequency with which gum disease and heart disease occur in the same patients, many dentists believe that periodontal disease is a cause of a variety of cardiovascular problems, including Coronary Artery Disease.

Which of the following, if true, would most weaken the claim that periodontal disease is a cause of Coronary Artery disease?

periodontal disease=>CAD

A. Bacteria present in infected gums can become mobile and enter the bloodstream, causing arterial plaque to accumulate. could strengthen
B. People who brush and floss their teeth regularly are also more likely to exercise and eat a healthy diet.
Weakens because it points away from the causal relationship established in the question stem.
C. Infected gums are more prone to bleeding, which allows bacteria to escape the mouth and irritate arteries.
could strengthen, but doesn't really relate to CAD specifically
D. People who experience loss of teeth due to periodontal disease usually cut back on many foods that are harder to chew, such as lean meats and vegetables, and increase their consumption of processed foods like pudding and ice cream.
could strengthen
E. Patients with no history of heart disease are much less likely to have periodontal disease than patients who have had a cardiac transplant. could strengthen, but starting with people with no history of heart disease are less likely to have periodontal disease isn't the best way to show that periodontal disease leads to heart disease
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Re: Citing the frequency with which gum disease and heart disease occur in  [#permalink]

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New post 11 Jul 2016, 19:16
can someone explain how B weakens the conclusion? B has absolutely 0 to do with anything in the stimulus
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Re: Citing the frequency with which gum disease and heart disease occur in  [#permalink]

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New post 21 Jul 2016, 14:01
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nycgirl212 wrote:
can someone explain how B weakens the conclusion? B has absolutely 0 to do with anything in the stimulus


The conclusion of the passage is periodontal disease is a cause of a variety of cardiovascular problems, i.e. disease of gum and teeth causes heart disease.

Option B states that people who take care of their teeth also live a healthy lifestyle. These people do not get heart disease not because they have healthy teeth, but because they lead healthy life.

The conclusion states a causal relation, whereas option B shows that the relation is not causal, but a correlation.

The logic chain can be thought of as follows:
Conclusion: X causes Z
Weakening statement: X and Y happen together, and Y causes Z. (i.e. X does not cause Z)

Here X = healthy teeth
Z = healthy heart
Y = healthy lifestyle.
Re: Citing the frequency with which gum disease and heart disease occur in &nbs [#permalink] 21 Jul 2016, 14:01

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