LNAT Evaluating Argument Strengths 2 — Questions and Answers
Question 1: An argument concludes that banning fast food near schools will reduce childhood obesity because children cannot access it during school hours. Which flaw best describes this reasoning?
- It assumes correlation implies causation
- It ignores that children can access fast food outside school hours (Correct answer)
- It uses an appeal to authority
- It presents a false dilemma
Correct answer: It ignores that children can access fast food outside school hours
The argument ignores that the restriction only applies during a fraction of children's daily time, leaving ample opportunity for access.
Question 2: A politician argues: 'Crime rates fell after we hired more police, so more police caused the crime reduction.' This argument is weakened most by which consideration?
- The politician may have a vested interest in the police force
- Other factors, such as economic improvement, may have caused the reduction (Correct answer)
- Crime statistics are always unreliable
- The argument uses emotional language
Correct answer: Other factors, such as economic improvement, may have caused the reduction
Post hoc reasoning mistakes temporal sequence for causation; other concurrent changes could explain the crime reduction.
Question 3: Which of the following most strengthens the argument that mandatory helmet laws reduce cycling fatalities?
- Cyclists who wear helmets tend to be more experienced
- Countries that introduced mandatory helmet laws saw immediate drops in cycling deaths (Correct answer)
- Helmets are uncomfortable and reduce cycling participation
- Some fatal accidents occur at speeds helmets cannot protect against
Correct answer: Countries that introduced mandatory helmet laws saw immediate drops in cycling deaths
Direct evidence of fatality reductions following the introduction of mandatory helmet laws provides strong causal support.
Question 4: A company claims its supplement is effective because 80% of users reported feeling better. What is the primary weakness of this evidence?
- The sample size is not stated
- It relies on self-reported outcomes without a control group (Correct answer)
- The company has a financial interest in the result
- Feeling better is not a medically recognized outcome
Correct answer: It relies on self-reported outcomes without a control group
Without a control group, it is impossible to separate the supplement's effect from the placebo effect or natural recovery.
Question 5: Argument: 'No evidence of harm has been found, so the chemical must be safe.' This reasoning exemplifies which fallacy?
- Slippery slope
- Ad hominem
- Appeal to ignorance (Correct answer)
- Straw man
Correct answer: Appeal to ignorance
An appeal to ignorance treats the absence of evidence as positive evidence of safety, which is logically invalid.
Question 6: A researcher finds that students who eat breakfast score higher on tests. She concludes breakfast causes better performance. Which additional finding would most weaken her conclusion?
- The tests were administered in the morning
- Wealthier students are more likely to eat breakfast and also have better study resources (Correct answer)
- Some students who skip breakfast still perform well
- The researcher did not account for sleep duration
Correct answer: Wealthier students are more likely to eat breakfast and also have better study resources
If socioeconomic status correlates with both breakfast eating and study resources, it could be the real cause of higher scores.
Question 7: Which principle underlies the idea that a strong inductive argument can still have a false conclusion?
- Inductive arguments are always invalid
- The premises of an inductive argument only make the conclusion probable, not certain (Correct answer)
- Inductive arguments require more than two premises
- A false premise automatically produces a false conclusion
Correct answer: The premises of an inductive argument only make the conclusion probable, not certain
Inductive reasoning yields probabilistic conclusions; even well-supported inductive conclusions can be overturned by new evidence.
