LSAT Logical Reasoning : Determining the flaw in the argument

Study concepts, example questions & explanations for LSAT Logical Reasoning

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Example Questions

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Example Question #1 : Flaw

Basketball scout: Over the last 25 years, every professional basketball player who was at least 6 feet 6 inches tall could dunk a basketball. Maurice will begin his professional basketball career this coming year and his amatuer team lists him as 6 feet 7 inches tall. Thus, Maurice definitely will be able to dunk.

The basketball scout’s argument is most vulnerable to which one of the following objections?

Possible Answers:

The argument relies on data provided by Maurice's amatuer team without examining the reliability of such data.

The argument infers that a characteristic of a certain subset of basketball players is shared by all basketball players.

The argument misinterprets evidence that a result is likely as evidence that the result is certain.

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

The argument mistakes a condition sufficient for bringing about a result for a condition necessary for doing so.

Correct answer:

The argument misinterprets evidence that a result is likely as evidence that the result is certain.

Explanation:

25 years of data is pretty good evidence that players standing at least 6 feet, 6 inches tall are likely to be able to dunk. However, the possibility always exists that Maurice is an outlier and can't dunk or that circumstances have changed and the last 25 years are not indicative of what will happen in the future (e.g., maybe basket heights have been raised by 2 feet, making it more difficult to dunk). Thus, certainty as to Maurice's dunking ability is not possible based on the evidence presented.

Example Question #2 : Flaw

Jim: My friends say I am putting my life in danger by snowboarding recklessly. But I have done some research, and apparently skiers have much lower accident rates than snowboarders. So, trading in my snowboard for a a pair of skis would lower my risk of having an accident.

Jim’s argument is most vulnerable to criticism on which of the following grounds?

Possible Answers:

The argument relies on information from a source that may be biased.

The argument relies on a sample that is too narrow.

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

The argument fails to take into account that Jim's friends are medical professionals.

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

Correct answer:

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

Explanation:

The fact the skiers have lower accident rates than snowboarders may not have any bearing on whether either activity is safer for Jim. That is, just because skiing is more correlated with safety than snowboarding does not mean that skiing is inherently safer than snowboarding; it is possible that skiers, as a group, tend to act less recklessly than snowboarders making the activity appear safer. In such a scenario, if Jim continues his reckless ways as a skier, he may be no better off than if he had continued to snowboard.

Example Question #1 : Determining The Flaw In The Argument

The statement "all blue birds are birds" is true. Thus, by analogy, the statement "all suspected terrorists are terrorists" is also true.

The reasoning in the argument above is flawed because it fails to recognize that

Possible Answers:

The relationship between being a bird and being a terrorist is not of the same kind as that between being blue and being suspected.

Not all terrorists are suspected

Not all birds are blue.

The relationship between being a blue bird and being a bird is not of the same kind as that between being a suspected terrorist and being a terrorist.

The relationship between being a bird and being suspected is not of the same kind as that between being blue and being a terrorist.

Correct answer:

The relationship between being a blue bird and being a bird is not of the same kind as that between being a suspected terrorist and being a terrorist.

Explanation:

It’s true that all blue birds are certainly birds — blue birds are a subset of the larger set of all birds. But a suspected terrorist may not be a terrorist at all. Just because "blue" and "suspected" are both used as adjectives to modify nouns does not mean that they modify the nouns in the same way.

Example Question #4 : Flaw

Modern medicine has taken a turn for the worse. Doctors prescribe treatments that can cause serious side effects. The ailments that doctors treat have existed for many years. Yet, the treatments prescribed are novel and dangerous. Treatment side effects cause not only things like itchy eyes or upset stomachs, but rather, depression, heart failure, and damaged immune systems. Natural remedies are preferable because they have been used widely for thousands of years. Also, most natural remedies carry comparatively low risk of serious side effects.

The argument is most clearly flawed for which of the following reasons?

Possible Answers:

The argument draws an overly broad conclusion

The argument assumes a preference for treatments that have existed for a longer time than treatments that are newer

The argument offers no reason why natural remedies are preferable to modern treatments

The argument fails to address whether natural remedies cause side effects as severe as those of modern treatments

The argument relies heavily on an appeal to emotion

Correct answer:

The argument assumes a preference for treatments that have existed for a longer time than treatments that are newer

Explanation:

The argument asserts that natural remedies cause less severe side effects than modern medical treatments, but it also makes an independent argument that natural remedies have been around for a long time. Without additional information, there is no support for concluding that one thing is better than another because it has been used for a longer time.

Example Question #5 : Flaw

Groups that oppose action to reduce emission of gases that contribute to global warming have major incentives to deny the existence of global warming. Many of these groups are backed by wealthy individuals or corporations that have a lot to lose from a new regulatory regime governing greenhouse gas emissions. This makes it likely that these groups’ publications will contain inaccurate information or misrepresent scientific evidence about global warming.

This argument is most vulnerable to the criticism that it:

Possible Answers:

Relies on the fact that a group has an incentive to produce inaccurate research as proof that their research is faulty.

Relies on a metaphor that is not applicable.

Assumes without providing justification that global warming is caused by humans.

Does not show that supporters of regulation on global warming do not have similar incentives to confirm the existence of global warming.

Does not lay out the argument for why global warming is correct.

Correct answer:

Relies on the fact that a group has an incentive to produce inaccurate research as proof that their research is faulty.

Explanation:

The argument criticizes the group making the argument not the argument itself. That is a classsic ad hominem argument that is flawed. The correct answer points this out.

Example Question #6 : Flaw

History Student: A widely held historical view of the Battle of Fort Sumter at the outbreak of the American Civil War is that President Lincoln deployed a strategy of reinforcement without direct military provocation to enable the Union to blame the outbreak of war on the Confederacy. One renowned historian has recently staked a controversial position that there is not enough evidence to justify this theory. Therefore, the widely held view of the outbreak of the Civil War is false.

The reasoning above is most vulnerable to the criticism that it:

Possible Answers:

Does not provide enough background to support its conclusion.

Overvalues the opinion of one historian.

Relies on an ambiguous use of the term false.

Takes the fact the lack of evidence that something is true as evidence that it is false.

Fails to clarify the qualifications of the renowned historian.

Correct answer:

Takes the fact the lack of evidence that something is true as evidence that it is false.

Explanation:

The stimulus does not provide evidence that the position of most historians is false just that there is not enough evidence to prove it true. Only the correct answer shows that critical flaw with the arguments construction.

Example Question #7 : Flaw

Computers have finally reached their maximum potential for processing information.  For fifty years, computer processing capabilities have steadily improved each year.  Although some years saw greater advancements than others, each year saw at least some progress.  That pattern was broken last year when computer processing capabilities failed to improve at all.

The argument is most vulnerable to which of the following criticisms?

Possible Answers:

It fails to account for the possibility that information processing capabilities improved somewhat over the last year, even though there has been greater improvement in other years

It fails to address the possibility that some of the previous fifty years saw no progress in information processing capabilities

It assumes, without providing support, that if information processing capabilities fail to improve in a given year, those capabilities cannot improve in the future

It assumes, without providing support, that if information processing capabilities improve in a given year, those capabilities have not reached their maximum potential

It assumes that computer processing capabilities failed to make any progress over the last year.

Correct answer:

It assumes, without providing support, that if information processing capabilities fail to improve in a given year, those capabilities cannot improve in the future

Explanation:

The argument's primary assertion is that information processing capabilities will not improve in the future (have reached maximum potential). It supports this by claiming that no advancements were made last year, but fails to address why that claim supports the conclusion. That there have been advancements in years past is not enough without an additional premise.

Example Question #8 : Flaw

The new music genre, “Eastern Vibe” has elements of different music genres. It has influences from Electronica, Dub Step, Rock, and Pop in its composition. Since it has no element in its composition that is original, it follows that the composition of “Eastern Vibe” cannot be considered original.

Which one of the following is a reasoning error made in the argument?

Possible Answers:

generalizing the instances of a few to all instances.

assuming that because something is true of each of the parts of a whole it is true of the whole itself.

deriving a conclusion from preferences rather than evidence.

interpreting a factor as a necessity rather than as a want.

presupposing what is to be proved by contradicting a claim.

Correct answer:

assuming that because something is true of each of the parts of a whole it is true of the whole itself.

Explanation:

The author argues that the new musical genre copied elements of other genres and is therefore not original. This argument does not necessarily follow as there could be other elements of the genre that are original such as the use of new instruments and sounds or the amalgamation of different sounds to form a new coherent genre. Therefore, something can be true of a whole without it being true of its parts; thus the author makes the error described in the answer choice: “assuming that because something is true of each of the parts of a whole it is true of the whole itself.”

Example Question #9 : Flaw

Doctor X: I disagree with Doctor Y’s proposed treatment plan for Mr. Jones. Doctor Y recommends that Mr. Jones undergo surgery because he is in substantial pain. However, Mr. Jones cannot afford to pay for the procedure or the cost of the hospital stay.

The reasoning in Doctor’s X’s argument is flawed because the argument:

Possible Answers:

does not take into account the comforts and amenities of the hospital where the procedure will be performed

fails to analyze the issue presented in terms of what is best for the patient

uses evidence concerning the economic feasibility of acting on a recommendation as a basis for questioning of the validity of the recommendation

engages in ad hominen attacks

compares the use of short-term versus long-term analysis

Correct answer:

uses evidence concerning the economic feasibility of acting on a recommendation as a basis for questioning of the validity of the recommendation

Explanation:

Doctor X only focuses on whether Mr. Jones can afford the procedure and does not discuss the medical merits of Doctor Y’s recommendation. Therefore, there is a scope shift. In other words, just because Mr. Jones cannot afford Doctor Y’s recommendation does not mean that his recommendation is suspect. This is reflected in the correct answer choice that states Doctor X’s flawed argument, “uses evidence concerning the economic feasibility of acting on a recommendation as a basis for questioning of the validity of the recommendation.”

Example Question #10 : Flaw

Mayor: Critics of the Healthy Eating Bill are delaying passage of this important law because they disagree with the more narrow definition of the term “unhealthy foods.” However, this legislation will place stricter limits on the type of foods that will be available to the public than our current laws. Therefore, by splitting hairs over semantics, these critics show their apathy to the public’s health.

The Mayor’s reply to the opponents of the Healthy Eating Bill is most vulnerable to which of the following criticisms?

Possible Answers:

 It attempts to defend the reputation of the author of Bill rather than the merits of the actual Bill.

It fails to adequately recognize the possibility that the definition of the term “unhealthy foods” determines the impact of the legislation.

It labels the critics of the Bill as supporters of the fast food industry.

It connects the motives of those who oppose the bill with the motives of those who produce soda.

It assumes that does who seek to defeat the Bill will profit from its defeat.

Correct answer:

It fails to adequately recognize the possibility that the definition of the term “unhealthy foods” determines the impact of the legislation.

Explanation:

The Mayor’s statement that the critics are “splitting hairs over semantics” indicates that he does not believe that the definition of the term "unhealthy foods" makes a difference to the argument. However, this is only his opinion. In actuality, a more restrictive, narrow definition of the term “unhealthy foods” may make significant difference to the critics of the bill. For example, a definition that excludes foods reputedly considered harmful to the public such as one that includes high fructose corn syrup or trans fat would not have the same impact as one that does; thus, support or criticism for the bill could turn on the definition of “unhealthy foods.” Therefore, the correct choice is: “It fails to adequately recognize the possibility that the definition of the term “unhealthy foods” determines the impact of the legislation.”

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