Medium LSAT Inference Questions With Answers Practice Questions

Concept Explanation

Inference questions on the LSAT require you to identify a statement that must be true or is most strongly supported based strictly on the provided information. Unlike assumption questions, which look for a missing link in an argument, inference questions ask you to look downward from the stimulus to find a valid conclusion. These questions test your ability to synthesize multiple facts without making unwarranted leaps or introducing outside information. In the context of LSAT Prep, medium-level inference questions often involve formal logic, conditional statements, or overlapping percentages that require careful tracking of quantity and possibility.

To solve these effectively, you must distinguish between what is likely and what is proven. According to the Law School Admission Council (LSAC), logical reasoning relies on identifying the relationship between premises. On the LSAT, an inference is not a "guess" or a "hunch"; it is a logical consequence. If the stimulus says "All A are B" and "Some A are C," you can infer that "Some B are C." You should avoid answer choices that use overly strong language—such as "all," "never," or "always"—unless the stimulus provides absolute support for such claims. Instead, look for "soft" language like "some," "many," or "can," which is easier to prove true.

Solved Examples

Review these worked examples to understand how to combine premises into a valid inference.

1. Example: Every student who studies for more than ten hours a week earns an A. Some students who earn an A also participate in extracurricular activities. No student who participates in extracurricular activities has a full-time job.
   Solution:
   1. Identify the chains: $\text{Study } > 10 \rightarrow \text{Earn A}$.
   2. Connect the overlaps: $\text{Some Earn A} \rightarrow \text{Extracurricular}$.
   3. Apply the negative: $\text{Extracurricular} \rightarrow \text{No Full-time Job}$.
   4. Inference: Some students who earn an A do not have a full-time job. (This must be true because those A-students in extracurriculars cannot have full-time jobs).
2. Example: If the city council approves the new park, the local tax rate will increase. If the local tax rate increases, the mayor will lose the upcoming election. However, the mayor is currently leading in the polls by a wide margin.
   Solution:
   1. Map the conditional: $\text{Park} \rightarrow \text{Tax Increase} \rightarrow \text{Mayor Loses}$.
   2. Contrapositive: If the Mayor does NOT lose (wins), then the tax rate did NOT increase and the park was NOT approved.
   3. Inference: If the mayor wins the upcoming election, the city council did not approve the new park.
3. Example: Most birds in the sanctuary are migratory. Some migratory birds in the sanctuary are endangered species. All endangered species in the sanctuary are monitored by drones.
   Solution:
   1. Quantify the terms: "Most" means $> 50\%$. "Some" means $\geq 1$.
   2. Link the groups: Endangered $\rightarrow$ Monitored.
   3. Combine: Since some migratory birds are endangered, and all endangered birds are monitored, then some migratory birds are monitored.
   4. Inference: At least some migratory birds in the sanctuary are monitored by drones.

Practice Questions

Test your skills with these Medium LSAT Inference Questions With Answers. Focus on what is strictly provable from the text.

1. High-fiber diets significantly reduce the risk of heart disease. However, most people who consume high-fiber diets also engage in regular exercise. It is well-documented that regular exercise independently reduces the risk of heart disease.

2. No professional athlete who uses banned substances is eligible for the Hall of Fame. Some athletes who are ineligible for the Hall of Fame are nevertheless highly respected by their peers. All athletes respected by their peers have high jersey sales.

3. If the temperature drops below freezing, the water pipes in the basement will burst unless they are insulated. The water pipes in the basement did not burst last night, even though the temperature dropped to $-5^{\circ} \text{C}$.

4. Most successful tech startups were founded by individuals under the age of 30. However, most tech startups that fail within the first two years were also founded by individuals under the age of 30.

5. Any company that prioritizes short-term profits over long-term sustainability will eventually face a liquidity crisis. Company X has never faced a liquidity crisis in its forty-year history.

6. All members of the chess club are also members of the debate team. No member of the debate team is enrolled in the advanced calculus seminar. Some students in the advanced calculus seminar are on the varsity swim team.

7. If a piece of legislation is popular with the public, it will be passed by the Senate. If the Senate passes a piece of legislation, the President will sign it into law unless it is deemed unconstitutional. The President did not sign the recent Clean Air Act into law.

8. Many species of tropical fish are sensitive to changes in water pH. Any fish sensitive to pH changes cannot survive in a standard home aquarium without specialized filtration. Some fish that require specialized filtration are expensive to maintain.

Answers & Explanations

1. Answer: It cannot be determined from the information provided whether high-fiber diets alone are responsible for the reduction in heart disease risk.
   Explanation: The stimulus presents a correlation (fiber and lower risk) but introduces a confounding variable (exercise). Because most fiber-consumers also exercise, we cannot isolate the cause.
2. Answer: Some athletes with high jersey sales are ineligible for the Hall of Fame.
   Explanation: We are told some ineligible athletes are respected, and all respected athletes have high sales. Therefore, that specific group of respected/ineligible athletes must have high sales.
3. Answer: The water pipes in the basement were insulated.
   Explanation: The rule is: $\text{Below Freezing} + \text{Not Insulated} \rightarrow \text{Burst}$. Since it was below freezing and they did NOT burst, the condition "Not Insulated" must be false.
4. Answer: Age of the founder is not a definitive predictor of a tech startup's success or failure.
   Explanation: Since both successful and failing startups are mostly founded by people under 30, the age factor does not distinguish one outcome from the other.
5. Answer: Company X has not prioritized short-term profits over long-term sustainability.
   Explanation: This is the contrapositive of the first sentence. If $A \rightarrow B$, then $\text{not } B \rightarrow \text{not } A$. Since no liquidity crisis occurred, the priority must have been sustainability.
6. Answer: No member of the chess club is enrolled in the advanced calculus seminar.
   Explanation: All chess members are in debate, and no debate members are in calculus. Therefore, no chess member can be in calculus.
7. Answer: Either the Clean Air Act was not popular with the public, or it was deemed unconstitutional.
   Explanation: If it were popular, it would pass the Senate. If it passed the Senate, the President would sign it UNLESS it was unconstitutional. Since he didn't sign it, either it never reached him (not popular) or the exception (unconstitutional) applied.
8. Answer: At least some fish that cannot survive in a standard aquarium without specialized filtration are expensive to maintain.
   Explanation: Some fish needing filtration are expensive. Since all pH-sensitive fish need filtration, the overlap exists within the group requiring specialized care.

Frequently Asked Questions

What is the difference between an inference and an assumption?

An inference is a conclusion that follows logically from the given premises, whereas an assumption is an unstated premise required to make an argument valid. Inferences look for what must be true based on the text, while assumptions look for what the author took for granted.

How do I handle "most" and "some" in LSAT inference questions?

Treat "some" as meaning "at least one" and "most" as meaning "more than half." You can often combine "most" and "all" to find an inference, but you generally cannot combine two "most" statements unless they refer to the same group and exceed 100% in total.

Can an inference be a restatement of a premise?

Technically, yes, because a restatement must be true if the original premise is true. However, the LSAT usually requires you to synthesize at least two pieces of information or identify the contrapositive of a conditional statement.

Why are strong words like "always" usually wrong in answer choices?

Strong words are difficult to prove unless the stimulus uses equally strong language. If a stimulus says "many people like coffee," you cannot infer that "everyone likes coffee," making moderate answer choices safer and more likely to be correct.

What is a contrapositive and why is it useful?

A contrapositive is a logically equivalent version of a conditional statement, created by flipping and negating both terms. If the stimulus says "If A, then B," the contrapositive "If not B, then not A" is a common source of correct inference answers.