Hard LSAT Strengthen Questions With Answers Practice Questions

Concept Explanation

LSAT strengthen questions require you to identify the piece of information that, if true, would most increase the probability that the argument's conclusion is logically valid. These questions focus on the relationship between the premises and the conclusion, often requiring you to bridge a logical gap or eliminate a potential weakness in the reasoning. On the LSAT Prep journey, these questions are considered high-priority because they test your ability to recognize structural vulnerabilities in an argument. Unlike assumption questions, which look for what is necessary for the argument to survive, strengthen questions look for what is helpful to make the argument more robust. A successful answer might provide a new piece of evidence, confirm a causal link, or rule out an alternative explanation that could otherwise undermine the conclusion.

Solved Examples

Reviewing these worked examples will help you understand the mechanics of identifying and supporting an argument's core logic.

1. Argument: Recent data shows that cities with more public parks have lower rates of respiratory illnesses. Therefore, the presence of trees and grass in these parks is directly responsible for cleaning the air and improving public health.
   Strengthener: A study found that cities with many parks do not have significantly lower levels of industrial pollution than cities with few parks.
   Step-by-Step Solution:
   1. Identify the conclusion: Trees and grass in parks cause the health improvement.
   2. Identify the potential weakness: Maybe these cities just have less pollution overall, which causes both the health benefit and the parks.
   3. Evaluate the strengthener: By showing that pollution levels are the same, we eliminate a major alternative explanation, making it more likely that the parks themselves (the trees and grass) are the cause.
2. Argument: The new software update was designed to reduce battery drain. Since the average battery life of users increased by 20% immediately after the update, the software must be effective.
   Strengthener: During the period after the update, there was no significant change in the types of hardware or apps the users were running.
   Step-by-Step Solution:
   1. Identify the conclusion: The software update caused the battery life increase.
   2. Identify the potential weakness: Perhaps users changed their habits or hardware at the same time.
   3. Evaluate the strengthener: This rules out variables like hardware changes, strengthening the causal link between the software and the result.
3. Argument: Archaeologists found charred remains of grains in a cave inhabited 15,000 years ago. Because these grains are not native to the region, the inhabitants must have traded with distant tribes.
   Strengthener: The climate of the region 15,000 years ago was not suitable for the natural growth of these specific grains.
   Step-by-Step Solution:
   1. Identify the conclusion: The grains were obtained through trade.
   2. Identify the potential weakness: Maybe the grains grew there naturally in the past even if they don't now.
   3. Evaluate the strengthener: Confirming the grains could not grow there naturally forces the conclusion that they had to be brought in from elsewhere.

Practice Questions

1. A tech company observed that employees who attend weekly yoga sessions report 30% less stress. The company concluded that yoga is the most effective way to improve employee mental health. Which of the following, if true, most strengthens the argument?
2. Economists argue that raising the minimum wage in City X will lead to higher unemployment because small businesses will be unable to afford the increased labor costs. Which of the following most strengthens the economists' prediction?
3. Marine biologists noted that coral reefs near tourist hubs are bleaching faster than those in remote areas. They conclude that chemical sunscreens worn by tourists are the primary cause of this degradation. Which of the following most strengthens the biologists' conclusion?

4. A historical novelist claims that King Richard III was actually a benevolent ruler because records show he funded three hospitals. Critics argue these records were forged by later supporters. Which of the following most strengthens the novelist's claim?
5. Traffic congestion in the downtown area has decreased since the introduction of a new toll for entering the city center. The city council claims the toll is the sole reason for the improvement. Which of the following most strengthens the council's claim?
6. Studies show that children who play musical instruments perform better on math tests. Researchers conclude that musical training develops the same spatial-temporal reasoning used in mathematics. Which of the following most strengthens this conclusion?
7. The bird population in the local wetlands has declined by 40%. Since a new housing development was built nearby last year, the development's construction must be the cause of the decline. Which of the following most strengthens the argument?
8. A new law requires all cyclists to wear helmets. Proponents argue this will significantly reduce the number of head injuries in the city. Which of the following, if true, most strengthens the proponents' argument?
9. A manufacturer claims their new glass is unbreakable because it survived a drop from a ten-story building. Which of the following most strengthens the manufacturer's claim?
10. A nutritionist claims that consuming blueberries improves memory in elderly patients. This is based on a study where participants who ate blueberries daily for a month scored higher on memory tests than those who did not. Which of the following most strengthens the claim?

Answers & Explanations

1. Answer: Employees who were already low-stress did not disproportionately choose to attend the yoga sessions.
   Explanation: This rules out reverse causality or self-selection bias, ensuring that yoga likely caused the stress reduction rather than low-stress people simply being the ones who had time or inclination for yoga.
2. Answer: Small businesses in City X currently operate on extremely thin profit margins that cannot absorb any additional expenses.
   Explanation: This provides evidence for the premise that businesses "cannot afford" the increase, making the predicted outcome of unemployment more certain.
3. Answer: Remote reefs with similar water temperatures and light levels as the tourist hubs are not experiencing significant bleaching.
   Explanation: By controlling for other common causes of bleaching (like temperature), this strengthens the case that the unique factor at the hubs—tourist activity/sunscreen—is the culprit.
4. Answer: Independent financial ledgers from local merchants during that era confirm large payments made by the crown to hospital staff.
   Explanation: This provides external validation for the disputed records, neutralizing the critics' objection.
5. Answer: There was no increase in the use of public transportation or remote work policies during the period the toll was implemented.
   Explanation: This rules out alternative explanations for the traffic decrease, leaving the toll as the most likely cause.
6. Answer: Children who started musical training showed immediate improvements in spatial-temporal tasks compared to a control group of children who started other hobbies.
   Explanation: This establishes a clearer temporal link and uses a control group to isolate musical training as the variable of change.
7. Answer: Bird populations in similar nearby wetlands without new housing developments remained stable during the same period.
   Explanation: This uses a comparison to show that the decline wasn't a regional trend, pointing specifically to the housing development as the local cause.
8. Answer: A majority of current head injuries among cyclists in the city occur at speeds where helmets are proven to be effective.
   Explanation: This connects the solution (helmets) to the specific nature of the problem (current injuries), ensuring the law will actually have the intended effect.
9. Answer: The glass was dropped onto a concrete surface and landed on its edge, the most vulnerable point for glass structures.
   Explanation: This demonstrates that the test was rigorous and not a fluke, strengthening the claim of "unbreakability."
10. Answer: The two groups of participants were identical in their baseline memory scores and lifestyle habits before the study began.
    Explanation: This ensures that the difference in scores was due to the blueberries and not pre-existing differences between the groups.

Frequently Asked Questions

What is the difference between a strengthen question and an assumption question?

An assumption is something the argument needs to be true to function, while a strengthener is something that helps the argument but isn't necessarily required. Think of an assumption as the foundation and a strengthener as an extra support beam.

Can a strengthen answer introduce new information not mentioned in the stimulus?

Yes, strengthen questions explicitly allow and often require new information to bridge logical gaps. You should treat the answer choices as if they are true and then see which one aids the argument most.

How do I handle causal strengthen questions?

To strengthen a causal claim, you can eliminate an alternative cause, show the cause and effect appearing together, or show that when the cause is absent, the effect is also absent. You can find more practice on logical structures in our reading analysis guides.

Should I look for an answer that makes the conclusion certain?

Not necessarily; the LSAT asks for the choice that "most strengthens." While an answer that makes the conclusion certain is a great strengthener, a choice that simply makes it more probable than it was before is often the correct one.

What are common wrong answer types for these questions?

Common traps include answers that weaken the argument, answers that are irrelevant, and "shell game" answers that look similar to the topic but discuss a slightly different concept or group. Using an AI Exam Simulator can help you learn to spot these patterns quickly.