SDCAR2010【逻辑入门】（九）Flaw (part 1)

sdcar2010

Prompts for Flaw questions:

• Which one of the following most accurately describes a flaw in the argument?
• The argument above is most vulnerable to criticism on the grounds that it . . .
• The reasoning in the argument is questionable because the argument . . .
  

Before you look at the answer:
1. Pinpoint the main conclusion in the passage. (Read my previous Main Point post.)
2. Separate the premises from everything else. After you find the main point, don’t assume that all the other statements are premises; they might include opposing viewpoints, background information, and concessions.
3. Ask yourself, “Do the premises, especially as they are stated in the passage, support the conclusion, especially as it is stated in the passage?” In other words, once you discard everything else, how well do the premises support the conclusion? The reason you want to focus on exactly what the premises and the conclusion state is that you do not want to subconsciously make the argument better than it actually is. Do not help the author. Look at what he actually said and then decide whether his evidence stacks up. (See “weaken” questions)

Make sure you are not reading anything into the conclusion that is not there. (“Thus, there is no evidence that Mar has life” is very different from “Thus, there is no life on Mars.”)

Wrong answers will often describe a flaw for a conclusion that the argument never actually reached. (For the conclusion saying that there is no evidence of life on Mars, the answer choice which states the argument “presumes, without providing justification, that the lack of evidence for a claim proves that the claim is false” would be wrong because the argument does not conclude that there is no life on Mars –only that there is no evidence of life on Mars.)

4. In your own words, describe the flaw. Try to avoid looking at the answers until you have forced yourself to describe at least one flaw or weakness in the stimulus.

Then look for the answer that most accurately describes what you described.

1. Focus on the active clause of each answer to help yourself move through the answers faster.

2. The correct answer must describe exactly what is happening in the passage. Make sure every word of that answer correlates with some part of the passage. In other words, translate the abstract terms into concrete terms from the passage. If there is only one example in the passage, for example, the answer choice with “examples” is probably wrong.

3. Check your answer by asking yourself, “If I remove this flaw, would that fix the argument?”

Common Flaws：

1. False contrapositives

• Negating both conditions without switching them.
• Switching both conditions without negating them.
• The correct answer will usually include one of these words: necessary, required, sufficient, or ensured.
  

If the law punishes littering, then the city has an obligation to provide trash cans. But the law does not punish littering, so the city has no such obligation.

Which one of the following exhibits a flawed pattern of reasoning most similar to that in the argument above?

(A) If today is a holiday, then the bakery will not be open. The bakery is not open for business. Thus today is a holiday.
(B) Jenny will have lots of balloons at her birthday party. There are no balloons around yet, so today is not her birthday.
(C) The new regulations will be successful only if most of the students adhere to them. Since most of the students will adhere to those regulations, the new regulations will be successful.
(D) In the event that my flight had been late, I would have missed the committee meeting. Fortunately, my flight is on time. Therefore, I will make it to the meeting.
(E) When the law is enforced, some people are jailed. But no one is in jail. So clearly the law is not enforced.

2. Causation

i) A happens before B does not mean that A causes B.

• Might be a coincidence
• Maybe C caused B
• Maybe C caused A and B
  

ii) A happens with B does not mean that A caused B.

• Might be a coincidence
• Maybe B caused A
• Maybe C caused B
• Maybe C caused A and B
  

iii) the correct answer will usually include one these words: cause or effect.

Driver: My friends say I will one day have an accident because I drive my sports car recklessly. But I have done some research, and apparently minivans and larger sedans have very low accident rates compared to sports cars. So trading my sports car in for a minivan would lower my risk of having an accident.

The reasoning in the driver's argument is most vulnerable to criticism on the grounds that this argument

(A) infers a cause from a mere correlation
(B) relies on a sample that is too narrow
(C) misinterprets evidence that a result is likely as evidence that the result is certain
(D) mistakes a condition sufficient for bringing about a result for a condition necessary for doing so
(E) relies on a sorce that is probably not well-informed

3. Attacking the author’s motive or actions, rather than the argument itself. Keep in mind that you need to focus on the logic stated in the argument, nothing else. Whether the author is angel or devil has no effect on the argument.

4. Attacking a weaker argument instead of the main conclusion: “What you are saying is that. . .”

5. Irrelevant authority

? Popular opinion. Most CDers think I am smart. Therefore, I am smart!
? Unqualified individuals. Since Yao Mng is a great athlete, if he says GMAT is a piece of cake, it probably is.
? Emotions.

6. Irrelevant premises

Ask yourself, “Do the premises strengthen or weaken the conclusion?” If not, they are irrelevant. Often premises will use the same words and thus appear relevant even though they are not.

7. Conflicting premise or assumptions

Example: “That family of four needs a dozen eggs to make a breakfast. Hua, the dad, did not buy enough eggs for his family because he bought only three eggs for each family member.”

At present the Hollywood Restaurant has only standard-height tables. However, many customers come to watch the celebrities who frequent the Hollywood, and they would prefer tall tables with stools because such seating would afford a better view of the celebrities. Moreover, diners seated on stools typically do not stay as long as diners seated at standard-height tables. Therefore, if the Hollywood replaced some of its seating with high tables and stools, its profits would increase.

The argument is vulnerable to criticism on the grounds that it gives reason to believe that it is likely that

(A) some celebrities come to the Hollywood to be seen, and so might choose to sit at the tall tables if they were available
(B) the price of meals ordered by celebrities dining at the Hollywood compensates for the longer time, if any, they spend lingering over their meals
(C) a customer of the Hollywood who would choose to sit at a tall table would be an exception to the generalization about lingering
(D) a restaurant's customers who spend less time at their meals typically order less expensive meals than those who remain at their meals longer
(E) with enough tall tables to accommodate all the Hollywood's customers interested in such seating, there would be no view except of other tall he support

8. Circular

Ask yourself, “Could the conclusion support the premises?” If so, then the argument is circular –it assumes what it is trying to prove.

SDCAR2010【逻辑入门】（八）Assumptions

SDCAR2010【逻辑入门】（十）Flaw (part 2)

Kb24

nice!

jianaozhonghua

没抢到沙发！  请问本系列什么时候截稿啊？   希望能在我考前啊。。。7月中旬  那样我逻辑就牛了  哈哈哈

Kb24

yeah you're late bro. haha!  great stuff though. combined with Lawyer's framework, this collection will help you kick GMAT logic's ass.....

perain

I wrote my answers for the sample answers after each questions:

If the law punishes littering, then the city has an obligation to provide trash cans. But the law does not punish littering, so the city has no such obligation.
Which one of the following exhibits a flawed pattern of reasoning most similar to that in the argument above?
(A) If today is a holiday, then the bakery will not be open. The bakery is not open for business. Thus today is a holiday.
(B) Jenny will have lots of balloons at her birthday party. There are no balloons around yet, so today is not her birthday.
(C) The new regulations will be successful only if most of the students adhere to them. Since most of the students will adhere to those regulations, the new regulations will be successful.
(D) In the event that my flight had been late, I would have missed the committee meeting. Fortunately, my flight is on time. Therefore, I will make it to the meeting.
(E) When the law is enforced, some people are jailed. But no one is in jail. So clearly the law is not enforced.
My answer: D.    ABCE seem to use the same pattern.


Driver: My friends say I will one day have an accident because I drive my sports car recklessly. But I have done some research, and apparently minivans and larger sedans have very low accident rates compared to sports cars. So trading my sports car in for a minivan would lower my risk of having an accident.
The reasoning in the driver's argument is most vulnerable to criticism on the grounds that this argument
(A) infers a cause from a mere correlation
(B) relies on a sample that is too narrow
(C) misinterprets evidence that a result is likely as evidence that the result is certain
(D) mistakes a condition sufficient for bringing about a result for a condition necessary for doing so
(E) relies on a sorce that is probably not well-informed
My guess is A, but I'm not sure... I don't quite understand what D means even though I translate it into Chinese...


At present the Hollywood Restaurant has only standard-height tables. However, many customers come to watch the celebrities who frequent the Hollywood, and they would prefer tall tables with stools because such seating would afford a better view of the celebrities. Moreover, diners seated on stools typically do not stay as long as diners seated at standard-height tables. Therefore, if the Hollywood replaced some of its seating with high tables and stools, its profits would increase.
The argument is vulnerable to criticism on the grounds that it gives reason to believe that it is likely that

(A) some celebrities come to the Hollywood to be seen, and so might choose to sit at the tall tables if they were available
(B) the price of meals ordered by celebrities dining at the Hollywood compensates for the longer time, if any, they spend lingering over their meals
(C) a customer of the Hollywood who would choose to sit at a tall table would be an exception to the generalization about lingering
(D) a restaurant's customers who spend less time at their meals typically order less expensive meals than those who remain at their meals longer
(E) with enough tall tables to accommodate all the Hollywood's customers interested in such seating, there would be no view except of other tall he support

Answer is C. When I saw this question for the first time, I chose D incorrectly. I think D can produce a gap because this option mentions the customers who spend less time at their meal instead of the customers who sit on the tall tables and stools.

sdcar2010

I wrote my answers for the sample answers after each questions:

If the law punishes littering, then the city has an obligation to provide trash cans. But the law does not punish littering, so the city has no such obligation.
Which one of the following exhibits a flawed pattern of reasoning most similar to that in the argument above?
(A) If today is a holiday, then the bakery will not be open. The bakery is not open for business. Thus today is a holiday.
(B) Jenny will have lots of balloons at her birthday party. There are no balloons around yet, so today is not her birthday.
(C) The new regulations will be successful only if most of the students adhere to them. Since most of the students will adhere to those regulations, the new regulations will be successful.
(D) In the event that my flight had been late, I would have missed the committee meeting. Fortunately, my flight is on time. Therefore, I will make it to the meeting.
(E) When the law is enforced, some people are jailed. But no one is in jail. So clearly the law is not enforced.
My answer: D.    ABCE seem to use the same pattern.


Driver: My friends say I will one day have an accident because I drive my sports car recklessly. But I have done some research, and apparently minivans and larger sedans have very low accident rates compared to sports cars. So trading my sports car in for a minivan would lower my risk of having an accident.
The reasoning in the driver's argument is most vulnerable to criticism on the grounds that this argument
(A) infers a cause from a mere correlation
(B) relies on a sample that is too narrow
(C) misinterprets evidence that a result is likely as evidence that the result is certain
(D) mistakes a condition sufficient for bringing about a result for a condition necessary for doing so
(E) relies on a sorce that is probably not well-informed
My guess is A, but I'm not sure... I don't quite understand what D means even though I translate it into Chinese...


At present the Hollywood Restaurant has only standard-height tables. However, many customers come to watch the celebrities who frequent the Hollywood, and they would prefer tall tables with stools because such seating would afford a better view of the celebrities. Moreover, diners seated on stools typically do not stay as long as diners seated at standard-height tables. Therefore, if the Hollywood replaced some of its seating with high tables and stools, its profits would increase.
The argument is vulnerable to criticism on the grounds that it gives reason to believe that it is likely that

(A) some celebrities come to the Hollywood to be seen, and so might choose to sit at the tall tables if they were available
(B) the price of meals ordered by celebrities dining at the Hollywood compensates for the longer time, if any, they spend lingering over their meals
(C) a customer of the Hollywood who would choose to sit at a tall table would be an exception to the generalization about lingering
(D) a restaurant's customers who spend less time at their meals typically order less expensive meals than those who remain at their meals longer
(E) with enough tall tables to accommodate all the Hollywood's customers interested in such seating, there would be no view except of other tall he support

Answer is C. When I saw this question for the first time, I chose D incorrectly. I think D can produce a gap because this option mentions the customers who spend less time at their meal instead of the customers who sit on the tall tables and stools.

-- by 会员 perain (2011/6/28 16:31:14)

Hurray. You got it ALL correct.

mistakes a condition sufficient for bringing about a result for a condition necessary for doing so

The above flaw is demonstrated in the following argument:
Premise: If event A, then event B
Conclusion: If event B, then event A.

guoqi

Hey, SDCAR2010,
I am reading your analysis of CR, they are really really really  good. Today, I just finished the section 9. There is a question that I didn't understand
even if I read your analysis of it. Here is the question.

At present the Hollywood Restaurant has only standard-height tables. However, many customers come to watch the celebrities who frequent the Hollywood, and they would prefer
tall tables with stools because such seatingwould afford a better view of the
celebrities. Moreover, diners seated on stools typically do not stay as long as diners seated at standard-height tables. Therefore, if the Hollywood replaced some of its seating with high tables and stools, its profits would increase.

The argument is vulnerable to criticism on the grounds that it gives reason to believe that it is likely that

(A) some celebrities come to the Hollywood to be seen, and so might choose to sit at the tall tables if they were available
(B) the price of meals ordered by celebrities dining at the Hollywood compensates for the longer time, if any, they spend lingering over their meals
(C) a customer of the Hollywood who would choose to sit at a tall table would be an exception to the generalization about lingering
(D) a restaurant's customers who spend less time at their meals typically order less expensive meals than those who remain at their meals longer
(E) with enough tall tables to accommodate all the Hollywood's customers interested in such seating, there would be no view except of other tall he supp

Here is your analysis
First of all, this is a paradox question and the question stem asks you to find the criticism.  So let's analyze the argument.

Premises:
1) Customers come to Hollywood Restaurant to watch the celebrities so customrs would prefer tall tables to get a better view.
2) Diners seated on stools typically stay a shorter time than diners on regular seats.

Conclusion:
If the Hollywood replaced some of its seating with high tables and stools, its profits would increase.

Basically, the argument says that stools would attract more customers and customers sitting on stools turn over quickly.  
Therefore, profits would be up.  Wait a minute.  Based on premise 1, if the customers are attracted to the restaraunt because they
want to see celebrities, shouldn't they stay LONGER than normal customers? If so, it runs contrary to premise 2 which describes
a general trend in customer's lingering behavior. The customer attracted might sit on the stools for a LONNNNNNNNNNNNNNG time without spending much on food. No turnover, no money!

C points out this paradox and C is the correct answer.    

                             
I have couple of questions for you and hope you can answer them. Thanks a lot.
No1  What you said here is that it is a must ture question, and we cann't use any new information. However, in your analysis, you said that "shouldn't they stay longer?" Isn't it a new information? The argument just said that they would like to watch celebrities, it doesn't mention the time at all.  They can stay here for 1 minute or 100 hours, maybe most of them are satisified with just staying with famous guys for few minutes, so we don't know that part at all. How can you use " shouldn't they stay longer" as a weapon to attack the premise 2?

2 I don't qutie understand the your logic here. You said "premise 2 which describes a general trend in customer's lingering behavior" . I checked the meaning of 'lingering" , it means "stay there longer than usual " and premise 2 indeed expresses that custoemrs will to saty there shorter. I am totally toally confused here. You said customers are staying longer whereas the argument said something different.

3 How to use Option C to solve this problem?  You sai C points out the paradox, how does it point out the paradox. What C says is that a customer would like to stay shorter and this behaviour is different form generalization of lingering. This means most of the people would like to stay longer. If most of customers would like to stay there longer, it proves Premise 2 is wrong. Is this the right logic?  

Thank you

sdcar2010

Good question and good comments.

Looking closely, I would label No. 9 as a flaw question, whose flaw is that it contains a paradox, or conflicting premises.

Lingering here is a noun, not an adjective. So lingering means sojourn, tarriance, or plainly, stay.

What C) says is:
a customer of the Hollywood who would choose to sit at a tall table (stay longer to view celebrities) would be an exception to the generalization about lingering (diners seated on stools typically do not stay as long as diners seated at standard-height tables).

As to stay longer to see the celebrities part, it is just common sense, albeit a tricky one.

C) does not attack premises. C) simply points out that both premises cannot be valid at the same time for the conclusion to hold. Individually, both premises are correct. But when you combine the two premises together, you cannot get the conclusion the argument tries to reach.

sdcar2010

Here is another flaw question:
Joseph: My encyclopedia says that the mathematician Pierre de Fermat died in 1665 without leaving behind any written proof for a theorem that he claimed nonetheless to have proved. Probably this alleged theorem simply cannot be proved, since---as the article points out---no one else has been able to prove it. Therefore it is likely that Fermat was either lying or else mistaken when he made his claim.
Laura: Your encyclopedia is out of date. Recently someone has in fact proved Fermat’s theorem. And since the theorem is provable, your claim---that Fermat was lying or mistaken---clearly is wrong.

Which one of the following most accurately describes a reasoning error in Laura’s argument?

(A) It purports to establish its conclusion by making a claim that, if true, would actually contradict that conclusion.
(B) It mistakenly assumes that the quality of a person’s character can legitimately be taken to guarantee the accuracy of the claims that person has made.
(C) It mistakes something that is necessary for its conclusion to follow for something that ensures that the conclusion follows.
(D) It uses the term “provable” without defining it.
(E) It fails to distinguish between a true claim that has mistakenly between believed to be false and a false claim that has mistakenly been believed to be true.

jaze

At present the Hollywood Restaurant has only standard-height tables. However, many customers come to watch the celebrities who frequent the Hollywood, and they would prefer tall tables with stools because such seating would afford a better view of the celebrities. Moreover, diners seated on stools typically do not stay as long as diners seated at standard-height tables. Therefore, if the Hollywood replaced some of its seating with high tables and stools, its profits would increase.


The argument is vulnerable to criticism on the grounds that it gives reason to believe that it is likely that

(A) some celebrities come to the Hollywood to be seen, and so might choose to sit at the tall tables if they were available
(B) the price of meals ordered by celebrities dining at the Hollywood compensates for the longer time, if any, they spend lingering over their meals
(C) a customer of the Hollywood who would choose to sit at a tall table would be an exception to the generalization about lingering
(D) a restaurant's customers who spend less time at their meals typically order less expensive meals than those who remain at their meals longer
(E) with enough tall tables to accommodate all the Hollywood's customers interested in such seating, there would be no view except of other tall he support

I really do not quite understand why the OA is C
My reasoning is this:
Background. However, premise, and intermediate conclusion because premise. Moreover, premise.
Therefore, premise, conclusion.

The author draws his conclusion based on two premise: one is the change will attract more people, and the other is people who seat at high tables will stay less time. That is, more people, higher fluidity.

(C) a customer of the Hollywood who would choose to sit at a tall table would be an exception to the generalization about lingering

I do not understand the relation between what option c says and what the premises says.
If the exception to the generalization about lingering can constrain people to seat at high table, then i know the Option can really weaken the conclusion. But what is reaction of people who would choose to sit at a tall table is not mentioned in the conclusion. I thought this answers is a relevant one.