LSAT Logical Reasoning : Determining which answer most accurately expresses the main idea of the argument

Study concepts, example questions & explanations for LSAT Logical Reasoning

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Example Questions

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Example Question #1 : Main Point / Main Conclusion

Doctor: A major study found no causal link between having received an MMR vaccine and having autism, but the study is flawed. The study looked at 500 people who had received an MMR vaccine. Because autism occurs in less than 1% of the population, researchers would need to include many more than 500 people in a study to detect a meaningful increase in the rate of autism.

Which of the following most accurately expresses the main conclusion of the doctor's argument?

Possible Answers:

A major study that discovered no causal relationship between the MMR vaccine and autism is unreliable.

Contrary to the findings of a major study, there is reason to believe that the MMR vaccine causes autism.

The major study cited does not reach a conclusion as to whether autism results from the MMR vaccine.

Medical professionals should conduct more research into the MMR vaccine to determine whether it is causally linked with autism.

Researchers cannot determine whether a given disorder is causally linked to a procedure if the base rate for the disorder is less than 1%.

Correct answer:

A major study that discovered no causal relationship between the MMR vaccine and autism is unreliable.

Explanation:

The passage begins with a fact and the judgment that the study is flawed. The rest of the paragraph explains how it's flawed (i.e., not enough people were included in the study to justify the conclusion). Therefore, the correct answer is the first sentence, because everything else in the passage supports that claim.

Example Question #2 : Main Point / Main Conclusion

While coffee does stain teeth, most claims that coffee has ill-effects are unfounded. There is even some evidence of health benefits. The situation may be different when the arguments relate to people who consume more than a moderate amount of coffee.

Which of the following conclusions most logically follows from the argument?

Possible Answers:

Moderate consumption of coffee has health benefits while excessive consumption causes ill-effects, including teeth staining

Moderate coffee consumption will not stain teeth

Many purported ill-effects from moderate consumption of coffee are unfounded

Consumed in moderation, coffee has no ill-effects

People who drink coffee in excess are likely to have severe teeth staining

Correct answer:

Many purported ill-effects from moderate consumption of coffee are unfounded

Explanation:

The argument does not draw a strong conclusion.  It does not assert that coffee is healthy or that it has no negative health effects. 

Example Question #1 : Main Point / Main Conclusion

We all have an obligation to do our part to protect nature. Only those who do are environmentally responsible. No people who insist on using incandescent light bulbs do their part to protect nature.

Which of the following conclusions follows:

Possible Answers:

Incandescent light bulbs cause harm to nature

All those who do not insist on using incandescent light bulbs are environmentally responsible

Incandescent light bulbs are only used by those who are environmentally irresponsible

People who insist on using incandescent light bulbs are not environmentally responsible

Environmentally responsible people have an obligation to discourage others from using incandescent light bulbs

Correct answer:

People who insist on using incandescent light bulbs are not environmentally responsible

Explanation:

Only people who do their part to protect nature are environmentally responsible.  Those who insist on using incandescent light bulbs do not do their part to protect the environment.  It follows that those who insist on using incandescent light bulbs are not environmentally responsible. 

Example Question #3 : Main Point / Main Conclusion

Taxpayers have been complaining about the U.S. tax system for many years. The tax system is so complex that very few can understand its provisions. A tax system that can only be understood by a very few people inefficiently generates revenue.

Which of the following is a logical conclusion to the argument?

Possible Answers:

The U.S. tax system inefficiently generates revenue because its complexity creates loopholes

The U.S. tax system generates revenue less efficiently than some other systems

Taxpayers complain about the U.S. tax system because it inefficiently generates revenue

Taxpayers would complain about the tax system less if it were less complex

The U.S. tax system inefficiently generates revenue

Correct answer:

The U.S. tax system inefficiently generates revenue

Explanation:

If the U.S. tax system can only be understood by a few, and tax systems that can only be understood by a few inefficiently generate revenue, then it follows that the U.S. tax system inefficiently generates revenue.

Example Question #2 : Main Point / Main Conclusion

Public transportaion plays less of a role in commuting within cities than it once did, which is unfortunate because the benefits for cities and residents are substantial.  Public transportation leads to less traffic congestion, more parking for those who do drive, less stress, less expense, and better air quality. Legitimate downsides to taking public transportation include safety concerns and lengthened commutes. Addressing these concerns would take effort but would also produce tremendous benefits.

Which of the following conclusions best follows from the argument?

Possible Answers:

While there are downsides to public transportation, they could be addressed and public transportation has benefits for both cities and residents

Public transportation is used less often in cities now than it once was because of safety concerns and longer commutes

It is difficult to explain why fewer people use public transportation than once did because the benefits are substantial for cities and city residents

While there are significant benefits to public transportation in cities, the substantial downsides explain why it is used less than it once was

If public transportation were used more widely, traffic in cities would run more smoothly and there would be other benefits as well

Correct answer:

While there are downsides to public transportation, they could be addressed and public transportation has benefits for both cities and residents

Explanation:

While the argument recognizes benefits of public transportation, it does not directly endorse its use, instead, recognizing legitimate downsides as well. On the other hand, the passage is clear that public transportation has real, positive implications for modern cities. Finally, the point of the argument is not to compare the present and past.

Example Question #101 : Lsat Logical Reasoning

The growth of coffee shops raises interesting questions about the desire to spend time with other people. Coffee shops are wildly popular but it is not clear why. Sure, people love coffee, but they don't need to sit in a coffee shop to drink it. Further, while coffee shops try to create pleasant study environments, it seems unlikely that people sit for hours for the music over the speakers and the pictures on the walls. Besides, as coffee shops have become more popular, public and school libraries have become less popular. Is it possible that the real coffee shop appeal is the opportunity to be around other people?

Which of the following most accurately states the primary point of the passage?

Possible Answers:

The atmosphere of coffee shops should be more appealing than that of libraries

It is unclear why coffee shops are so popular because they do not seem to have any unique advantages

Customers are drawn to coffee shops even though they are filled with other people and do not have uniquely appealing atmospheres

Coffee shops are more popular than they once were despite the fact that they appear to have little to offer customers

It is unclear why coffee shops are popular, but the answer could be that they provide a way for customers to be around other people

Correct answer:

It is unclear why coffee shops are popular, but the answer could be that they provide a way for customers to be around other people

Explanation:

The first and last sentences of the passage raise the issue of whether people attend coffee shops to be around other people. Instead of stating a firm conclusion, the purpose of the passage is to raise that possible explanation by ruling out others.

Example Question #102 : Lsat Logical Reasoning

The school needs to find new ways to improve its test scores. Although the school used to have a large amount of highly-qualified teachers, many of them have left to pursue other careers. Their departure has harmed the quality of instruction students receive. The school is unlikely to attract talented teachers in the near future.

Which one of the following most accurately presents the main conclusion of the passage?

Possible Answers:

The school needs to find new ways to improve its test scores.

The school’s test scores are suffering.

The school needs to attract new highly-qualified teachers.

The school is unlikely to attract talented teachers in the near future.

The departure of highly-qualified teachers has harmed the instruction the students receive.

Correct answer:

The school needs to find new ways to improve its test scores.

Explanation:

The first sentence is the conclusion. The rest of the stimulus is mearly support for that initial conclusion.

Example Question #2 : Main Point / Main Conclusion

While factory unions provide accountability for employers and job security for employees, they also present some hazards.  First, unions always increase costs of production by adding bureaucracy.  Second, unions sometimes serve the elitist purpose of providing high pay and benefits for union members while non-members fail to find any employment.

Which of the following is the most logical conclusion to the passage?

Possible Answers:

Unions provide valuable services, but sometimes increase costs of production and always serve elitist purposes.

Unions serve a valuable role, but sometimes increase costs of production and increase elitism.

Unions serve a valuable role, but also increase costs of production and sometimes increase elitism.

Unions provide critically important services to factory employees.

Unions sometimes cause the hazards of elitism and increased costs of production.

Correct answer:

Unions serve a valuable role, but also increase costs of production and sometimes increase elitism.

Explanation:

There are two keys to this question.  First, the passage does not reach a firm, positive or negative conclusion about unions, instead suggesting that there are considerations on both sides.  Second, the passage discusses two negative traits, but specifies that the first "always" occurs and the second "sometimes" occurs. 

Example Question #103 : Lsat Logical Reasoning

The Salem witch trials are often cited as an example of mob mentality.  There are many lessons to learn from the events, but fear of mob mentality is not one of them.  First, the entire process took place over an extended period of time.  Second, the leaders and participants carefully considered actions before they were taken.  In contrast, mob mentality generally describes actions that are not carefully considered and that end quickly.

Which of the following most accurately describes the main point of the passage?

Possible Answers:

Mob mentality describes actions that are not carefully considered and that end quickly

The Salem witch trials are not an example of mob mentality

The Salem witch trials demonstrate that even carefully considered actions can lead to tragic results

The Salem witch trials are an example of mob mentality

There are many important lessons to be learned from the Salem witch trials

Correct answer:

The Salem witch trials are not an example of mob mentality

Explanation:

The emphasis of the passage is on describing differences between the Salem witch trials and mob mentality.  That is the purpose of the passage.  The other assertions in the argument are intended to support the claim that the Salem witch trials are not an example of mob mentality.

Example Question #2 : Determining Which Answer Most Accurately Expresses The Main Idea Of The Argument

The political writer criticized the use of the term, "global warming," as he believes it can confuse the general public as to the reality of the climate change that the world is experiencing. The trends that we are seeing in climate change are not limited to increased temperatures in some areas, but also significantly decreased temperatures in others. The issue isn't the general "warming" of the globe, but its simultaneous warming and cooling. Based on these facts, the writer prefers the term "global weirding" to "global warming."

Which of the following most accurately describes the main point of the argument?

Possible Answers:

It is important to be precise in our use of language. 

Trends in climate change are only now beginning to come to light. 

Global cooling is just as severe of a problem as global warming. 

Terminology with inappropriate connotations can confuse the general public's understanding of important issues. 

Global warming is misunderstood by most people. 

Correct answer:

Terminology with inappropriate connotations can confuse the general public's understanding of important issues. 

Explanation:

The correct answer is:

Terminology with inappropriate connotations can confuse the general public's understanding of important issues. 

The writer believes that "global warming" is an inappropriate term because it makes people overlook the fact that global cooling is also a serious problem. The main point of the text is to communicate the problems that can arise when terminology with improper connotations is used in practice.  

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