How to Identify and Solve Flaw Questions on the LSAT

You can usually identify flaw questions by how they’re worded. Prompts often ask which answer “most accurately describes a flaw in the argument” or point out that the reasoning is “most vulnerable to criticism.” 

These questions are about identifying a specific logical mistake. The LSAT tests your ability to see through persuasive language and find the gaps between premises and conclusions.

To confidently solve flaw questions, you need a structured approach. Start by breaking down the argument into its conclusion and supporting premises. Ask yourself: what is the author trying to prove, and how are they trying to prove it? 

Next, look for common patterns of flawed reasoning. Some of the most frequent include mistaking correlation for causation, making overly broad generalizations, relying on circular reasoning, presenting false dilemmas, and confusing necessary and sufficient conditions. 

Once you've broken the argument apart and identified potential flaws, try to anticipate the flaw before reading the answer choices. This step prevents you from falling for tempting but incorrect options. Then, as you read through the choices, match their abstract phrasing to the specific flaw you identified. 

Pay close attention to wording; correct answers will often describe the flaw in precise, logical terms. If two answers seem plausible, go with the one that most directly and accurately pinpoints the flaw in reasoning.

10 Sample Flaw Questions on the LSAT With Answer Explanations

To better understand how these questions work, let’s walk through 10 sample flaw questions with brief explanations for the best LSAT strategies.

Sample Question #1

“All Labrador retrievers bark a great deal. All Saint Bernards bark infrequently. Each of Rosa’s dogs is a cross between a Labrador retriever and a Saint Bernard. Therefore, Rosa’s dogs are moderate barkers.”

Which one of the following uses flawed reasoning that most closely resembles the flawed reasoning used in the argument above?

(A) All students who study diligently make good grades. But some students who do not study diligently also make good grades. Jane studies somewhat diligently. Therefore, Jane makes somewhat good grades. 

(B) All type A chemicals are extremely toxic to human beings. All type B chemicals are nontoxic to human beings. This household cleaner is a mixture of a type A chemical and a type B chemical. Therefore, this household cleaner is moderately toxic. 

(C) All students at Hanson School live in Green County. All students at Edwards School live in Winn County. Members of the Perry family attend both Hanson and Edwards. Therefore, some members of the Perry family live in Green County and some live in Winn County. 

(D) All transcriptionists know shorthand. All engineers know calculus. Bob has worked both as a transcriptionist and as an engineer. Therefore, Bob knows both shorthand and calculus. 

(E) All of Kenisha’s dresses are very well made. All of Connie’s dresses are very badly made. Half of the dresses in this closet are very well made, and half of them are very badly made. Therefore, half of the dresses in this closet are Kenisha’s and half of them are Connie’s.

Answer:

A. This is a tempting option, but it falls short. It uses a vague “some” statement and fails to establish a clear link between lack of diligence and very bad grades. To parallel the stimulus, we’d need something like: Diligent students get good grades. Non-diligent students get bad grades. Therefore, somewhat diligent students get somewhat good grades. That structure isn't here.

B. CORRECT. This is a perfect match. The reasoning mirrors the original:
Type A = Labrador retriever (non-barker)
Type B = Saint Bernard (barker)
So a mix of the two leads to a dog that barks moderately, just like in the original argument, where the blend of two extremes produced a midpoint trait.

C. This doesn’t align. The original stimulus focused on individuals who are half of each type. This answer describes two different people from two places, rather than one person being half from each. A better match would be: “Each Perry family member lives half in Green County, half in Winn County.”

D. Close, but not quite. To match the flawed reasoning, this should say: “Transcriptionists write shorthand. Engineers write only calculus. Bob is half engineer, half transcriptionist—so he writes half shorthand, half calculus.” That would mirror the structure of combining traits from two distinct roles.

E. Like C, this fails to merge the traits within a single entity. It talks about different dresses, but doesn’t combine elements within one, as the stimulus did with the dog's behavior.

Sample Question #2

“Consumer: The latest Connorly Report suggests that Ocksenfrey prepackaged meals are virtually devoid of nutritional value. But the Connorly Report is commissioned by Danto Foods, Ocksenfrey’s largest corporate rival, and early drafts of the report are submitted for approval to Danto Foods’ public relations department. Because of the obvious bias of this report, it is clear that Ocksenfrey’s prepackaged meals really are nutritious.”

The reasoning in the consumer’s argument is most vulnerable to criticism on the grounds that the argument

(A) treats evidence that there is an apparent bias as evidence that the Connorly Report’s claims are false 

(B) draws a conclusion based solely on an unrepresentative sample of Ocksenfrey’s products 

(C) fails to take into account the possibility that Ocksenfrey has just as much motivation to create negative publicity for Danto as Danto has to create negative publicity for Ocksenfrey 

(D) fails to provide evidence that Danto Foods’ prepackaged meals are not more nutritious than Ocksenfrey’s are 

(E) presumes, without providing justification, that Danto Foods’ public relations department would not approve a draft of a report that was hostile to Danto Foods’ products

Answer:

A. CORRECT. This accurately identifies the flaw: the argument attacks the person (or company, in this case) rather than addressing the merits of the products. Classic ad hominem reasoning.

B. This isn’t about an unrepresentative sample. The consumer criticizes all of Ocksenfrey’s prepackaged meals, not just a select few. A true unrepresentative sample flaw would involve judging the whole based on a small, possibly biased, part.

C. While Ocksenfrey might be biased, that’s not the issue here. The consumer isn’t relying on any claims made by Ocksenfrey, so the company’s potential bias is irrelevant to the argument.

D. The argument makes no claims about Danto’s product quality. It focuses solely on criticizing Ocksenfrey. So this choice introduces information that isn’t part of the original reasoning.

E. This sounds appealing, but it misses the point. The consumer isn’t referring to reports about Danto, hostile or otherwise. They’re only referencing information about Ocksenfrey, so this doesn’t apply.

Sample Question #3

“Hospital executive: At a recent conference on nonprofit management, several computer experts maintained that the most significant threat faced by large institutions such as universities and hospitals is unauthorized access to confidential data. In light of this testimony, we should make the protection of our clients’ confidentiality our highest priority.”

The hospital executive’s argument is most vulnerable to which one of the following objections?

(A) The argument confuses the causes of a problem with the appropriate solutions to that problem. 

(B) The argument relies on the testimony of experts whose expertise is not shown to be sufficiently broad to support their general claim. 

(C) The argument assumes that a correlation between two phenomena is evidence that one is the cause of the other. 

(D) The argument draws a general conclusion about a group based on data about an unrepresentative sample of that group. 

(E) The argument infers that a property belonging to large institutions belongs to all institutions.

Answer:

A. This flaw doesn’t apply here.
Example: My house is on fire, so to solve the problem, I’ll set the fire itself on fire. This reflects a circular or self-defeating solution, not something present in the argument.

B. CORRECT. This identifies the flaw accurately. The argument relies on the opinion of computer experts without verifying whether they understand the full range of threats large organizations face. If their expertise is limited to computer-related issues, their assessment may overlook more serious non-digital threats.

C. This flaw didn’t occur.
Example: Computer hacking has increased since the invention of cars, so cars must be the cause. That’s a classic confusion of correlation with causation, which isn’t the reasoning used here.

D. This isn’t the issue.
Example: Bob is a computer expert from Arkansas, so all computer experts must be from Arkansas. That would be an unrepresentative sample flaw, but the argument doesn't generalize from a single case or a small group.

E. No overgeneralization is present.Example: Large corporations need HR departments, so your neighborhood corner store must have one too. This would be an unwarranted generalization from one context to another, but the argument doesn’t do that.

Sample Question #4

“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 source that is probably not well- informed

Answer:

A. CORRECT. This is the flaw in the argument. The driver assumes that minivans cause fewer accidents because they’re associated with a lower accident rate. But correlation doesn’t equal causation; it could be that safer drivers tend to choose minivans, and that’s what actually accounts for the lower accident rate.

B. This isn’t a sample flaw. The argument refers broadly to minivans and larger sedans, which seems like a reasonable comparison group. LSAT questions don’t flag sampling errors unless they explicitly mention small or biased samples (e.g., "my two friends..."). Without that, we assume the sample is adequate.

C. This is a different flaw entirely.
Example: I might win the lottery, so I bought a luxury car, because there's no doubt I’ll win. This reflects a leap from possibility to certainty, which the argument doesn’t make.

D. This is a mistaken reversal flaw, but it doesn’t apply here.
Example: If someone is in a car accident, they were in a car → Therefore, if someone is in a car, they will have an accident. That’s flawed logic, but not the reasoning used in this case.

E. The argument doesn’t question the source of the data. The driver claims they "researched accident rates," and there’s no reason to doubt that based on the stimulus. Under the principle of charity (used by LSAC), we interpret claims in a reasonable light, not as irrational or baseless unless the stimulus clearly indicates otherwise.

Sample Question #5

“Many corporations have begun decorating their halls with motivational posters in hopes of boosting their employees’ motivation to work productively. However, almost all employees at these corporations are already motivated to work productively. So these corporations’ use of motivational posters is unlikely to achieve its intended purpose.”

The reasoning in the argument is most vulnerable to criticism on the grounds that the argument

(A) fails to consider whether corporations that do not currently use motivational posters would increase their employees’ motivation to work productively if they began using the posters 

(B) takes for granted that, with respect to their employees’ motivation to work productively, corporations that decorate their halls with motivational posters are representative of corporations in general 

(C) fails to consider that even if motivational posters do not have one particular beneficial effect for corporations, they may have similar effects that are equally beneficial 

(D) does not adequately address the possibility that employee productivity is strongly affected by factors other than employees’ motivation to work productively 

(E) fails to consider that even if employees are already motivated to work productively, motivational posters may increase that motivation

Answer:

A. This one is tempting at first glance because it sounds similar to the correct answer. But it misses the mark. It talks about companies that don’t use motivational posters, while the stimulus only discusses companies that do use them. So this answer addresses the wrong group entirely.

B. The argument doesn't generalize to all corporations; it specifically refers to “these corporations” that use motivational posters and whose employees already report high motivation. So this answer overreaches and doesn’t match the scope of the conclusion.

C. This misrepresents the conclusion. The argument is focused solely on whether motivational posters increase motivation. It doesn’t claim that the posters have no other benefits, so this answer makes an unsupported assumption.

D. The author is talking about motivation to work productively, not productivity itself. That’s an important distinction; the argument measures intent or desire, not actual performance. This answer confuses the two.

E. CORRECT. This points out the core flaw. The argument assumes that because employees already report high motivation, the posters must not be helping. But it overlooks the possibility that the posters boosted motivation, from, say, 75 to 85, thus contributing to the high level. It ignores potential marginal gains, which undermines the conclusion.

Sample Question #6

“Some video game makers have sold the movie rights for popular games. However, this move is rarely good from a business perspective. After all, StarQuanta sold the movie rights to its popular game Nostroma, but the poorly made film adaptation of the game was hated by critics and the public alike. Subsequent versions of the Nostroma video game, although better than the original, sold poorly.”

The reasoning in the argument is most vulnerable to criticism in that the argument

(A) draws a general conclusion on the basis of just one individual case 

(B) infers that a product will be disliked by the public merely from the claim that the product was disliked by critics 

(C) restates as a conclusion a claim earlier presented as evidence for that conclusion (D) takes for granted that products with similar content that are in different media will be of roughly equal popularity 

(E) treats a requirement for a product to be popular as something that ensures that a product will be popular

Answer:

A. CORRECT. This identifies the flaw: the argument draws a broad conclusion based on a single example. To make a general claim about adaptations, you'd need more than just one failed movie to support it.

B. This contradicts the stimulus. The argument explicitly states that the movie was hated by both critics and the public. Also, the argument didn’t make a prediction, it evaluated an outcome that already happened.
Example of flaw: Critics disliked this video game, so the public will too.

C. This refers to circular reasoning, which didn’t happen here. Circular reasoning is rare and involves using a claim to prove itself.
Example: Selling movie rights is bad because it’s always a bad idea to sell movie rights.

D. This one is vague and doesn’t apply. It seems to reference flawed analogies, but the stimulus didn’t draw any cross-category comparisons.
Example of flaw: This movie with lots of sex scenes was a hit, so a video game with lots of sex scenes will be too.

E. This is about confusing sufficient and necessary conditions, which also doesn’t appear in the argument.Example: Good video games must be challenging. This game is challenging, so it must be good. That’s a classic mistaken reversal, but not relevant to this stimulus.

Sample Question #7

“Science writer: Lemaître argued that the universe began with the explosion of a “primeval atom,” a singular point of infinite gravity in space and time. If this is correct, our current observations should reveal galaxies accelerating away from one another. This is precisely what we observe. Yet because there is another theory—the oscillating universe theory—that makes exactly this same prediction, Lemaître’s theory must be considered inadequate.”

Which one of the following most accurately describes a flaw in the science writer’s reasoning?

(A) The conclusion is derived partly from assertions attributed to a purported expert whose credibility is not established. 

(B) The conclusion is based on a shift in meaning of a key term from one part of the argument to another part. 

(C) The science writer takes for granted the existence of a causal connection between observed phenomena. 

(D) The science writer fails to see that one theory’s correctly predicting observed data cannot itself constitute evidence against an alternative theory that also does this. 

(E) The science writer presumes, without providing justification, that there are only two possible explanations for the phenomena in question.

Answer:

A. The argument doesn’t bring up the credentials or expertise of the person who proposed the other theory, so that’s irrelevant. The key point is that the rival theory also fits the observational data, so expertise isn’t part of the argument’s logic.

B. This refers to a shift in meaning, but there's no evidence of that here. To pick this kind of flaw, you'd need to clearly identify a term used with one meaning early on and a different meaning later. That doesn’t happen in this argument.

C. There's no assumption of causation here.
Example of flaw (that didn’t occur): The light flickered, and a noise followed. Therefore, the light caused the noise. The argument doesn’t confuse correlation with causation.

D. CORRECT. This gets right to the flaw. Both theories make the same predictions and match the data equally well. So the author can't use the fact that Lemaitre’s theory fits the data as evidence against the other theory. They’re on equal footing in terms of support.

E. The author never claims these are the only two possible theories. They simply claim Lemaitre’s theory is correct and the rival is not. There's no reasoning flaw in limiting the field of possibilities.Example of flaw (that didn’t occur): These two theories both work, so they must be the only valid theories. That’s not what’s happening here.

Sample Question #8

“Party X has recently been accused by its opposition, Party Y, of accepting international campaign contributions, which is illegal. Such accusations are, however, ill founded. Three years ago, Party Y itself was involved in a scandal in which it was discovered that its national committee seriously violated campaign laws.”

Which one of the following contains flawed reasoning most similar to the flawed reasoning in the argument above?

(A) The plaintiff accuses the defendant of violating campaign laws, but the accusations are ill founded. While the defendant’s actions may violate certain laws, they are not immoral, because the laws in question are unjust. 

(B) The plaintiff accuses the defendant of violating campaign laws, but these accusations show the plaintiff to be hypocritical, because the plaintiff has engaged in similar conduct. 

(C) The plaintiff accuses the defendant of violating campaign laws, and, in the past, courts have declared such violations illegal. Nevertheless, because the plaintiff recently engaged in actions that were similar to those of the defendant, the plaintiff’s accusations are ill founded. 

(D) The plaintiff accuses the defendant of violating campaign laws, but these accusations are ill founded. They are clearly an attempt to stir up controversy, because they were made just two weeks before the election. 

(E) The plaintiff accuses the defendant of voting only for campaign laws that would favor the defendant’s party. This accusation is ill founded, however, because it attacks the defendant’s motivations instead of addressing the arguments the defendant has put forth justifying these votes.

Answer:

A. This is a weak argument, but it’s not an ad hominem flaw. The key issue here is that the legality of an action is distinct from its morality. Even if it’s debatable whether breaking the law is immoral, it is still clearly illegal. The argument conflates legal status with moral status.

B. This is actually a strong argument. If someone violates a law and then criticizes another for the same violation, they’re being hypocritical. But in the stimulus, the accusation wasn’t about hypocrisy, it was that Party Y was wrong, which is a separate claim. So this doesn’t match.

C. CORRECT. This mirrors the flawed reasoning in the stimulus. It argues that someone’s accusation is wrong solely because they also committed the same act. But even if the plaintiff is guilty of the same violation, that doesn’t prove their claim is false. Guilt doesn’t cancel out accuracy.

D. This is a bad argument, but again, not an ad hominem. It dismisses the accusation based on the motivation behind it (to stir up controversy), rather than addressing the claim’s validity. That’s a flaw, but a different one.

E. Another poor argument, but not an ad hominem. It wrongly assumes that if someone benefits from a law they support, that’s somehow improper. But even if they benefit, their support could still be legitimate. This doesn’t attack the person, it confuses self-interest with wrongdoing.

Sample Question #9

“Reformer: A survey of police departments keeps track of the national crime rate, which is the annual number of crimes per 100,000 people. The survey shows no significant reduction in the crime rate in the past 20 years, but the percentage of the population in prison has increased substantially, and public expenditure on prisons has grown at an alarming rate. This demonstrates that putting more people in prison cannot help to reduce crime.”

A flaw in the reformer’s argument is that it 

(A) infers without justification that because the national crime rate has increased, the number of crimes reported by each police department has increased 

(B) ignores the possibility that the crime rate would have significantly increased if it had not been for the greater rate of imprisonment 

(C) overlooks the possibility that the population has increased significantly over the past 20 years 

(D) presumes, without providing warrant, that alternative measures for reducing crime would be more effective than imprisonment 

(E) takes for granted that the number of prisoners must be proportional to the number of crimes committed

Answer:

A. The author never made this claim.
Example of flaw: The national crime rate rose, so our small town’s crime rate must have also risen, even though our only known criminal retired. This flaw involves assuming what's true of the whole must be true of the part, which isn’t the issue in the stimulus.

B. CORRECT. This exposes the flaw in the argument. The reformer concludes that jail time doesn’t reduce crime because the crime rate hasn’t dropped. But it’s entirely possible crime would have increased without jail time, so jail may be keeping the rate stable, which the argument fails to consider.

C. Population size isn’t the issue. Crime rate accounts for population, so it’s typically expressed per capita. If the population increases, the number of crimes may rise too, but the rate could stay the same. So this answer misses the point.

D. The reformer didn’t claim that other crime reduction strategies would work better. Their argument focused solely on the claim that jail doesn’t reduce crime. Whether other measures exist or succeed is irrelevant to their conclusion.

E. This is off-base. The argument doesn’t assume anything about proportionality between crimes and prisoners.Example of flaw (not present here): There were 5 crimes and 3 prisoners last year. This year, 10 crimes, so we must have 6 prisoners. That kind of rigid proportional reasoning isn’t used in the stimulus.

Sample Question #10

“Marketing consultant: Last year I predicted that LRG’s latest advertising campaign would be unpopular with customers and ineffective in promoting new products. But LRG ignored my predictions and took the advice of a competing consultant. This season’s sales figures show that sales are down and LRG’s new products are selling especially poorly. Thus, the advertising campaign was ill conceived.”

The marketing consultant’s reasoning is most vulnerable to criticism on the grounds that

(A) it takes for granted that LRG’s sales would not have been lower still in the absence of the competitor’s advertising campaign 

(B) it fails to consider that economic factors unrelated to the advertising campaign may have caused LRG’s low sales figures 

(C) it takes for granted that in LRG’s industry, new products should outsell established products 

(D) it takes for granted that the higher sales of established products are due to effective advertising 

(E) it confuses a condition necessary for increasing product sales with a condition that will ensure increased sales

Answer:

A. This one is tempting, but ultimately incorrect. Saying sales would have been "lower still" implies the campaign had no effect whatsoever, not even a single sale. But the consultant isn't claiming the campaign was completely ineffective, just that it wasn't particularly effective.
Example of flaw: Sales were low after the new ad campaign, so it must not have led to a single sale. That’s too strong a claim for the actual argument.

B. CORRECT. This identifies the core flaw. The consultant blames the ad campaign for poor sales, without considering other possible contributing factors, like product quality, pricing, or economic conditions. Even a strong campaign might not boost sales if other variables are unfavorable.

C. The argument never claims that newer campaigns are inherently more successful.
Example of flaw (not present): This new smartphone will outsell older models just because it’s newer.

D. The author doesn’t compare two products and attribute sales differences solely to advertising.
Example of flaw (not present): The old, popular brand outsells the new one, so its ad campaign must be better.

E. This describes a sufficient vs. necessary flaw, which isn’t at play here.
Example of flaw: To sell well, a product must be well-advertised. This product has good ads, so it will definitely sell well. That’s not the reasoning used in the stimulus.

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