LSAT Logic Reasoning 2 — Questions and Answers
Question 1: A researcher claims: 'All studies that used large sample sizes found significant results. This study used a large sample size. Therefore, this study found significant results.' Which flaw does this argument commit?
- It confuses correlation with causation.
- It affirms the consequent by assuming the conclusion follows necessarily. (Correct answer)
- It relies on an appeal to authority.
- It commits a hasty generalization from one case.
Correct answer: It affirms the consequent by assuming the conclusion follows necessarily.
The argument is invalid because 'all studies with large samples found significant results' does not guarantee any one new study will — it affirms the consequent.
Question 2: Which of the following, if true, most weakens the argument that banning cell phones in schools improves student grades?
- Schools that banned phones also hired additional tutors during the same period. (Correct answer)
- Students in schools with phone bans reported feeling less distracted.
- Phone use during class has been linked to lower test scores in multiple studies.
- Teachers at schools with phone bans received extra training.
Correct answer: Schools that banned phones also hired additional tutors during the same period.
If schools also hired tutors, the grade improvement may be due to tutoring rather than the phone ban, undermining the causal claim.
Question 3: Premise 1: If a contract is signed under duress, it is voidable. Premise 2: This contract is voidable. Conclusion: This contract was signed under duress. The conclusion is flawed because:
- Contracts can be voidable for reasons other than duress. (Correct answer)
- Duress is not a legal concept recognized in contract law.
- The premises contradict each other.
- The argument uses circular reasoning.
Correct answer: Contracts can be voidable for reasons other than duress.
The argument invalidly assumes duress is the only cause of voidability; other grounds (e.g., fraud, incapacity) also make contracts voidable.
Question 4: All of the following strengthen the argument that urban green spaces reduce crime rates EXCEPT:
- Neighborhoods with parks show lower vandalism rates than those without.
- Residents near green spaces report stronger community ties.
- Cities that built parks saw simultaneous increases in policing budgets. (Correct answer)
- Research shows that vegetation reduces stress-related aggressive behavior.
Correct answer: Cities that built parks saw simultaneous increases in policing budgets.
Increased policing, not green spaces, could explain the crime reduction, so this fact does not strengthen the green-space-crime link.
Question 5: A politician argues: 'We should not cut the defense budget because our nation's security depends on military strength.' This argument is best described as:
- A valid deductive argument with true premises.
- Circular reasoning that restates the conclusion as a premise. (Correct answer)
- An ad hominem attack on critics of defense spending.
- A slippery slope claiming cuts will lead to invasion.
Correct answer: Circular reasoning that restates the conclusion as a premise.
Saying security depends on military strength is essentially another way of saying we should not cut defense — the premise just re-expresses the conclusion.
Question 6: If a survey finds that 80% of lottery winners report being happy one year after winning, which of the following most undermines using this as evidence that money causes happiness?
- The survey had a large sample size of 500 winners.
- Unhappy winners may have been less likely to respond to the survey. (Correct answer)
- The survey was conducted by an independent research institution.
- Happiness was measured using a validated psychological scale.
Correct answer: Unhappy winners may have been less likely to respond to the survey.
If unhappy winners didn't respond, the 80% figure is inflated by response bias, undermining the causal inference.
Question 7: The statement 'No valid argument can have a false conclusion' is:
- True, because validity guarantees truth of the conclusion.
- False, because a valid argument can have a false conclusion if the premises are false. (Correct answer)
- True, because sound arguments are always valid.
- False, because invalid arguments sometimes produce true conclusions.
Correct answer: False, because a valid argument can have a false conclusion if the premises are false.
A valid argument guarantees only that IF the premises are true the conclusion is true; with false premises, the conclusion can still be false.
LSAT Logic Reasoning 2
A researcher claims: 'All studies that used large sample sizes found significant results.
This study used a large sample size.
Therefore, this study found significant results.' Which flaw does this argument commit?