Logical Flaw Flashcards
Flaw in reasoning vs Method of reasoning?
Flaw in the Reasoning questions are exactly the same as Method of Reasoning questions with the important exception that the question stem indicates that the reasoning in the stimulus is flawed.
This information provides you with a tremendous advantage because you can identify the error of
reasoning in the stimulus before proceeding to the answer choices.
And, if you did not realize there was an error of reasoning in the stimulus, the question stem gives you the opportunity to re-evaluate the argument and find the error of reasoning.
Question stem Keywords for “logical flaw”
- The reasoning is fallacious
- The reasoning is flawed
- Argiment is vulnerable to criticism
What do you do & clue for:
Logical flaw/weaken hybrid questions
correct ans points out a vulnerability in the argument + brings in new info that weakens
Clue: Which of the following, If true, points to the logical flaw
What family model does logical flaw belong to?
First Family (prove model) where the passage is used to prove the answer choice
The correct answer will identify the error in the author’s reasoning and then describe that error in general terms without adding any new info.
Beware of answers that describe a portion of the stimulus but fail to identify the error in the reasoning.- meaning we dont need an answer that just describes what the argument does without highlighting the flaw. This is a TRAP!
What is the strategy to master flaw in reasoning in GMAT?
- Identify common errors of reasoning in every passage you read: If you learn the mistakes that are often made by authors, then you will be able to quickly identify the error in the argument and accelerate through the answer choices to find the correct answer
- Identify common correct & incorrect answer choices: the test makers tend to use certain types of answers again and again. Familiarizing yourself with these answer choices will give you an advantage when you encounter similar answer choices in the future.
Types of incorrect answer choices in logical flaw.
- Describes something the argument doesnt do
- Describe something the argument does but that is not a flaw
- Describe a flaw in support of the wrong conclusion
- Brings up maths info that seem to matter but doesnt matter.
What do you do in this situation..
At your first glance of the passage, the argument looks very strong to you, but then you read the question stem and realize there must be an error in reasoning.
This is a critical moment: when the question stem indicates an error is present but you did not realize one exists, you must go back to the stimulus and look for the error.
Do not proceed to the answer choices thinking that the answers will clarify or reveal the error to you!
The answer choices are designed to subtly draw your attention toward side issues, and it is far preferable that you find the error first and then find the answer that correctly describes the error.
List 20 common errors of reasoning …
- Equivocation
- Source argument
- Circular reasoning
- Conditional reasoning errors
- Cause and effect Flaw
- Straw man
- irrelevant evidence for conclusion
- Self contradiction
- Sampling bias
- Overgeneralization
- Apeal fallacy
- False analogy
- False dichotomy
- Unproven vs untrue
- Porbability vs certainty
- Number & Percentage errors
- Weak/insufficent evidence
- Relative vs absolute
- Opinion vs Fact
- Time shift errors
- Slipery slope
- Part vs whole
Explain Logical flaw type:
Equivocation: Using a word with multiple meanings interchangeably.
Example: “Banks are safe. River banks are safe, so all banks are safe”
Flaw: This shift in meaning undermines the author’s position.
Clue: Uses the same word multiple times but in different contexts.
Examples of how this error of reasoning is described in
answer choices:
“equivocates with respect to a central concept”
“depending on the ambiguous use of a key term”
“it confuses two different meanings of the word ‘solve’ ”
“relies on interpreting a key term in two different ways”
“allows a key term to shift in meaning from one use to the next”
“fails to define the term”
Explain Logical flaw type:
Source argument: Attacking the person
(or source) instead of their argument.
A source argument can take different forms;
- Focusing on the motives of the source suggesting personal bias
Example: As the CEO of a fast‐food chain, Ms. Ramirez’s statement that processed foods are as healthy as fresh produce likely reflects her desire to boost sales rather than objective nutritional science. - Focusing on the actions of the source
Example: The anti-smoking views expressed by Senator Smith should be ignored. After all, Smith himself is a smoker!
Flaw: Focuses on source credibility, not evidence.
A speaker can never validly attack the character or motives of a person; instead, a speaker must always attack the person’s argument.
Clue: Accuses someone of hypocrisy or of personal bias
Examples of how this error of reasoning is described in answer choices:
“makes an attack on the character of opponents”
“it is directed against the proponent of a claim rather than against the claim itself”
“he directs his criticism against the person making the argument rather than directing it against the argument itself”
“it draws conclusions about the merit of a position and about the content of that position from evidence about the position’s source”
“assuming that a claim is false on the grounds that the person defending it is of questionable character”
Explain Logical flaw type:
Circular reasoning: Using the conclusion as a premise, creating a self-justifying loop. i.e the premise supports the conclusion, but the conclusion equally supports the premise, creating a “circular” situation
Example: “I must be telling the truth because I’m not lying.”
Flaw: No external evidence supports the claim
Clue: Premise and conclusion are saing the same thing.
Examples of how this error of reasoning is described in answer choices:
“it assumes what it seeks to establish”
“argues circularly by assuming the conclusion is true in stating the premises”
“presupposes the truth of what it sets out to prove”
“the argument assumes what it is attempting to demonstrate”
“it takes for granted the very claim that it sets out to establish”
“it offers, in place of support for its conclusion, a mere restatement of that conclusion”
Explain Logical flaw type:
Conditional reasoning error: The argument treats a conditional statement like it can be reserved or negated.
- Mistaken negation
- Mistaken reversal
- Confuses necessary for sufficient
- Confuses sufficient for necessary.
*Clue: conditional indicators (if/then) in stimulus
*Tip: if you identify a stimulus with conditional reasoning and are asked a Flaw question, you can quickly scan the answers for the one answer that contains “sufficient,” “necessary,” or both.
“taking the nonexistence of something as evidence that a necessary precondition for that thing also did not exist” (Mistaken Negation)
“mistakes being sufficient for being required” (Mistaken Reversal)
Explain Logical flaw type:
Cause and effect Flaw: Assuming that because two events occur together or sequentially, one causes the other.
- Causal flaw based on sequence of events.
- Causal flaw based on correlation
- Causal flaw based on co-occurence
- Failure to consider an alternate cause for the effect, or an alternate cause for both the cause and the effect.
- Failure to consider that the events may be reversed.
- Failure to consider events as mere coincidence
Clue: Cause and effect argument with cause-effect indicators
Tip: If you identify a stimulus with causal reasoning and are asked a Flaw question, quickly scan the answers for one that contains “cause,” “effect,” or both.
Temporal relationship = time sequence ie one thing happining after another
Explain Logical flaw type:
Straw Man: author ignores the actual statements made by the opposing speaker and instead distorts/misrepresents/refashions the argument, making it easier to attack.
Example:
Politician A: “The platform proposed by my party calls for a moderate increase in taxes on those individuals making over $20,000 per year, and then taking that money and using it to rebuild
the educational system.”
Politician B: “But what you’re saying is that everyone should pay higher taxes, and so your proposal is unfair.”
Flaw: Distorts the original argument
Clue: author argues against a claim the other side didn’t make.
Examples of how this error of reasoning is described in answer choices:
“refutes a distorted version of an opposing position”
“misdescribing the student representative’s position, thereby making it easier to challenge”
“portrays opponents’ views as more extreme than they really are”
“distorts the proposal advocated by opponents”
Explain Logical flaw type:
Irrelevant evidence for the conclusion: Author fails to provide any information to support their conclusion or they provide information that is irrelevant to their conclusion
Example: “Some critics claim that scientific progress has increased the polarization
of society and alienated large segments of the population. But these critics are wrong because even a cursory glance at the past shows that
society is always somewhat polarized and some groups are inevitably alienated.”
Flaw: Citing data that does not prove his argument or disprove the opposing argument, hence irrelevant.
Clue: evidence does not affect (S or W) the conclusion in any way.
Examples of how this error of reasoning is described in answer choices:
“The author cites irrelevant data.”
“draws a conclusion that is broader in scope than is warranted by the evidence advanced”
“It uses irrelevant facts to justify a claim about the quality of the disputed product.”
“It fails to give any reason for the judgment it reaches.”
“It introduces information unrelated to its conclusion as evidence in support of that conclusion.”
Explain Logical flaw type:
Self contradiction: author makes conflicting statements that contradict itself.
Example: “Everyone should join our country club. After all, it’s an exclusive
group that links many of the influential members of the community.”
Flaw: introduce information that actually contradicts the conclusion.
Clue: Author contradicts himself
“bases a conclusion on claims that are inconsistent with each other”
“the author makes incompatible assumptions”
“introduce information that actually contradicts the conclusion”
“offers in support of its conclusion pieces of evidence that are mutually contradictory”
“some of the evidence presented in support of the conclusion is inconsistent with other evidence provided”
“assumes something that it later denies, resulting in a contradiction”
Explain Logical flaw type:
Appeal Fallacies: author cites an authority outside their area of expertise or popular opinion or emotion in an attempt to pursuade reader
1. Apeal to authority (injustified)
E.g: “World-renowned neurologist Dr. Samuel Langhorne says that EZBrite Tooth Strips are the best for whitening your teeth. So, you know if you buy EZBrite you will soon have the whitest
teeth possible!”
Flaw: authority may not have relevant knowledge or all the information
regarding a situation.
2. Appeal to popular opinion
E.g: A recent poll states that 75% of Americans believe that Microsoft is a monopoly. Antitrust law states that monopolies have a deleterious effect on the marketplace (with the exception
of utilities), and therefore Microsoft should be controlled or broken into smaller pieces.”
Flaw: does not present a logical reason for accepting a position, just an appeal based on numbers.
3. Appeal to emotion
E.g: “Officer, please do not give me a ticket for speeding. In the last month I’ve been fired from my job, kicked out of my apartment, and my car broke down. I don’t deserve this!
Flaw: appeals to emotion rather than reason
Clue: uses popular opinion/emotion/unjustified authority to convice
Explain Logical flaw type:
Sampling Bias: Author draws conclusions from a non-representative or skewed data set.
Example: Example: “A survey of regular customers found our restaurant is the best in town.”
Flaw: uses evidence drawn from a small sample that may well be unrepresentative/bias. In other words, the survey respondents were not average
Clue: the argument itself includes a survey/study/poll to conclude.
“generalizes from an unrepresentative sample”
“states a generalization based on a selection that is not representative of the group about which the generalization is supposed to hold true”
Explain Logical flaw type:
Overgeneralization: Author drawing a broad conclusion from too small or limited evidence.
Example: “Three patients had side effects from a vaccine, so it’s unsafe.”
Flaw: takes a small number of instances and treats those instances as if they support a broad, sweeping conclusion
“supports a universal claim on the basis of a single example”
“The argument generalizes from too small a sample of cases”
“Too general a conclusion is made about investing on the basis of a single experiment”
“bases a general claim on a few exceptional instances”
Explain Logical flaw type:
False Analogy: An author compares two situations that are not sufficiently similar or uses an analogy that too dissimilar to the original situation to be applicable.
Example: “Just as a heavy rainfall can be cleansing, the best approach to maintain
a healthy relationship is to store up all your petty grievances and then unload them all at one time on your partner.”
FLaw: treats as similar two cases that are different in a critical respect
Explain Logical flaw type:
False Dilemma/Dichotomy: Author assumes that only two courses of action are available when there may be others
Example: “Recent accidents within the oil industry have made safety of operation
a critical public safety issue. Because the industry cannot be expected to police itself, the government must step in and take action.”
Flaw: falsely assumes that only two courses of action exist, and ignores the existence of possibilities.
Clue: Either / Or logic without evidence suggesting both cant occur
Note - Do not confuse a False Dilemma with a situation where the author legitimately establishes that only two possibilities exist. Phrases such as “either A or B will occur, but not both” can establish a limited set of possibilities, and certain real- world situations yield only two possibilities, such as “you are either dead or alive.”
Explain Logical flaw type:
Unproven vs Untrue: Lack of evidence to prove a position means that that position is false or Lack of evidence against a position means that the position is true
Example:
“Nobody has seen it. It could not have happened”.
“The study that reached conclusion X was flawed, therefore conclusion X is false”
Flaw: Argues based on ignorance. Lack of evidence/ability to prove ≠ does not exist/is not true.
Clue: prsnts lack of evidence/flaw in study as justification for untrue
Explain Logical flaw type:
Part vs. Whole: argument ascribes characteristics of a group to each member of that group, or states that because each part of something has a characteristic, the whole must have that characteristic.
Example:
“Every party I attend is fun and exciting. Therefore, my life is fun and exciting.
“The United States is the wealthiest country in the world. Thus, every American is wealthy.”
Clue: The argument talks about groups and individuals.
Explain Logical flaw type:
Possible vs. Certain: Argues that something is likely to happen therefore it will definitely happen.
Example: Sheila is likely to be in the party. Clearly, she will definitely be there.
Flaw: Likely ≠ guaranteed/certain
unlikely ≠ Uncertain
Clue: The premise of the argument deals with a possibility.
