LSAT Logical Reasoning : Determining which answer is an assumption which justifies the conclusion of the argument
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Example Questions
Example Question #1 : Sufficient Assumption
Live theater has been in competition with more modern media options for years. Today, there are a vast number of entertainment options and there is easy access to high quality entertainment technology, such as sophisticated home theater systems. Fewer people watch live theater than in the past. As a result, live theater has lost the competition with modern media.
Which of the following, if true, would allow the conclusion to be logically drawn?
Some people who once attended live theater now use sophisticated home theater systems
Live theater performances are not performed as often as they once were
Live theater has lost the competition with modern media only if it has fewer viewers than in the past
Home theater systems provide the same entertainment quality as live theater
In the past, there were very few entertainment options other than live theater
Live theater has lost the competition with modern media only if it has fewer viewers than in the past
The argument concludes that live theater has lost a competition with modern media. The conclusion does not logically follow from the assertions in the argument as they are presented. It is not clear how the competition would be lost. The additional premise allows the conclusion to be drawn.
Example Question #2 : Sufficient Assumption
Relaxation of credit standards helped cause the recent mortgage crisis. Credit standards should not have been relaxed because, if they had not been, the mortgage crisis would have been avoided.
The argument assumes which of the following?
Relaxation of credit standards would not have resulted in a crisis more severe than the mortgage crisis
The mortgage crisis could have been avoided despite relaxation of credit standards
The mortgage crisis would not have been caused by other factors
Most people were harmed by the mortgage crisis
There were no other sufficient causes of the mortgage crisis
There were no other sufficient causes of the mortgage crisis
The argument mentions the relaxation of credit standards as a cause of the mortgage crisis. It assumes that it is the only cause (or but for cause) of the crisis.
Example Question #3 : Sufficient Assumption
Movie producers complain that movie critics find it easier to write reviews about movies they dislike than to write reviews about movies that they like. Regardless of whether this hypothesis is true, most movie reviews are devoted to movies that critics find distasteful. Therefore, most movie reviews are devoted to movies other than the best movies.
The conclusion above is properly drawn if which of the following is assumed?
A movie that garners attention from critics can become more widely known than if it had not received this attention.
None of the movie critics likes to write about movies that they find extremely distasteful.
The greatest movies are not recognized until after the death of the movie producer.
The best movies are those that critics find tasteful.
All movie critics have difficulty finding movies that they find tasteful.
The best movies are those that critics find tasteful.
This argument misses the important link between critics not liking a movie and that movie not being one of the best movies. However, this conclusion would be valid if we have the assumption provided in the correct answer choice, “The best movies are those that critics find tasteful.” This assumption links the best movies with the movies that critics find tasteful. Thus, with this assumption, the conclusion works: If most movie reviews are devoted to movies that critics find distasteful, and the best movies are the movies that critics find tasteful, then it follows that most criticism is devoted to movies other than the best movies.
Example Question #4 : Sufficient Assumption
At this school, there are no ballet dancers who are also salsa dancers. However, all ballroom dancers are also salsa dancers. Therefore, no ballroom dancers will be competing in the upcoming competition.
The conclusion above follows logically if which one of the following is assumed?
No ballet dancers are also ballroom dancers.
Everyone who will compete in the upcoming competition is a salsa dancer.
Everyone who will compete in the upcoming competition is a ballet dancer.
Everyone who will compete in the upcoming competition is not a ballet dancer.
Some salsa dancers will compete in the upcoming competition.
Everyone who will compete in the upcoming competition is a ballet dancer.
We already know from the premises that ballroom dancers and ballet dancers are mutually exclusive. The only question that remains is who will compete in the upcoming competition. If only ballet dancers will compete, ballroom dancers are excluded (as well as salsa dancers), and the conclusion must logically follow.
Example Question #5 : Sufficient Assumption
The general contractor working on the new bridge should use caution before hiring subcontractors because many subcontractors defraud general contractors who do not take appropriate caution. When general contractors take appropriate caution, however, they always avoid being defrauded. The general contractor working on the new bridge will not be defrauded because he has formal contracts with his subcontractors.
Which of the following assumptions, if true, allows the conclusion to be properly drawn?
Some general contractors take appropriate caution without obtaining formal contracts
Some general contractors who obtain formal contracts are defrauded
General contractors are only sometimes defrauded
Some contractors who take appropriate caution also obtain formal contracts
Obtaining a formal contract is appropriate caution
Obtaining a formal contract is appropriate caution
We know that if there is appropriate caution, general contractors are not defrauded. We also know that the general contractor in this case obtained formal contracts. If obtaining formal contracts is appropriate caution, then the contractor here has taken appropriate caution and will not be defrauded.
Example Question #6 : Sufficient Assumption
A paleontologist found a dinosaur tibia and fibula bone group that was too large to be placed into a stabilized storage chest. Luckily, an assistant discovered a way to safely separate the tibia and fibula bones. These bones could be reassembled later without a noticeable change in either bone. Now the bones can be placed in two stabilized storage chests.
The argument above depends on which of the following assumptions?
Neither the tibia or fibula bone is too large to fit into the chest.
Placing the bones into the chest does not alter the accuracy of a later carbon-14 dating.
The tibula and fibula bone group can be separated into two equal sized parts.
The optimal conditions for preservation of the bones are found in the stabilized storage chest.
The procedure for using two chests does not cost more money than using just one vault.
Neither the tibia or fibula bone is too large to fit into the chest.
Here, size offered the only barrier to putting the tibia and fibula bone group into the chest. Since the separated bones can now fit into their own separate chests, the author assumes that each bone can fit into a chest. Thus, the correct choice is: “Neither the tibia or fibula bone is too large to fit into the chest.”
Example Question #7 : Sufficient Assumption
Large numbers of people fall ill every year from illnesses that could have been avoided by proper vaccination. Therefore, the government should spend money to educate people about the importance of getting vaccinated.
Which of the following assumptions would NOT support the argument?
Many vaccinations are not affordable for the average citizen.
People trust the government when it comes to decisions about their health.
The cost of an education campaign is less than the cost of treating the illness.
Many people are unaware of the availability and purpose of vaccinations.
The government has a duty to keep its citizens from becoming ill.
Many vaccinations are not affordable for the average citizen.
If the average citizen simply cannot afford vaccinations, then the government's expenditure of money on educating citizens may not be the wisest use of funds. The rest of the answer choices support the argument that the government should invest in an education campaign about vaccination.
Example Question #8 : Sufficient Assumption
The best obedience training new dog owners can undertake is training themselves. If the owner is disciplined, careful, and alert, the natural willingness to please in the puppy will follow right after the owner's own behavior and the puppy will become a well-trained dog.
Which one of the following is a sufficient assumption for the conclusion of the argument?
Obedience training for dogs only teaches certain tasks.
The toughest part of any dog obedience class is the beginning.
All dogs need to go through obedience training.
The hardest obedience tasks can only be learned by adult dogs.
All dogs innately wish to please their owners.
All dogs innately wish to please their owners.
The argument revolves around how to best train a dog in an obedience class, specifically saying that a well-trained human is the best vehicle for a well-trained dog; however, the main point that this argument hinges on, and which is not said directly in the statement, is that a dog is naturally adept at being trained through its innate wish to please its owner.
Example Question #1 : Sufficient Assumption
The most serious criminal offenders need to be placed in extra-secure prisons. Communications, even when well-searched and analyzed, are susceptible to sending secret messages to people not under incarceration, especially in the case of gang leaders, mafia members, and drug kingpins.
Which of the following is a sufficient assumption for the conclusion of the passage?
Gang leaders, mafia members, and drug kingpins are able to communicate well in code.
Prison security is based mostly around the smuggling of material inside to prisoners.
Prisons have no problems in monitoring communications from their inmates.
Most prisons are extremely secure, especially regarding communication outside of the prison.
The problem of prison security needs to be addressed in a multitude of ways.
Gang leaders, mafia members, and drug kingpins are able to communicate well in code.
The passage focuses on one aspect of prison security, communications in and out of prisons, and argues that tighter monitoring of that aspect is a necessity. While there are many assumptions that could lead to this conclusion, certain prisoners being more adept at codes would be sufficient to reach the idea that prisons are not as secure as they could be.
Example Question #9 : Assumption
Scientists are now reporting that recent studies show the drug has been extremely effective in masking the harmful side effects of the disease. This breakthrough gives hope to many patients that scientists are very close to finding an appropriate medicine to fully cure the disease.
Which of the following statements is a sufficient assumption for the argument in the above passage?
The sufferers of the disease were most concerned about the side effects, rather than curing the disease itself.
Curing the disease itself is much more important than treating the side effects
Scientists will be able to find the cure for the disease with the research they have already done.
The cure for the disease is related to the treatment of the side effects of the disease.
Very few scientists would have been able to find a treatment for the side effects of the disease.
The cure for the disease is related to the treatment of the side effects of the disease.
The passage states that the cure for the disease should come to pass soon, and that it will happen because there have now been breakthroughs in treating the disease's side effects. This indicates that it assumed that the two events are highly related, which is the sufficient assumption for the conclusion in the passage.
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