LNAT Science 5 ā Questions and Answers
Question 1: A passage describes an experiment where rats given high doses of artificial sweetener developed tumours. The author concludes the sweetener is dangerous for humans. What is the primary weakness of this conclusion?
- The experiment should have used a larger number of rats
- High-dose animal results cannot automatically be extrapolated to typical human consumption levels or human physiology (Correct answer)
- The study should have been conducted in a hospital setting
- Tumours in rats are always irrelevant to human health research
Correct answer: High-dose animal results cannot automatically be extrapolated to typical human consumption levels or human physiology
Extrapolating from extreme doses in a different species to typical human intake ignores dose-response relationships and interspecies physiological differences.
Question 2: Two scientists analyse the same climate dataset and reach opposite conclusions. Which of the following is the most scientifically sound response to this disagreement?
- Accept the conclusion of the more senior scientist
- Commission additional independent analyses and examine methodological differences between the two studies (Correct answer)
- Discard both studies as unreliable
- Accept the conclusion that supports current government policy
Correct answer: Commission additional independent analyses and examine methodological differences between the two studies
Scientific disagreement is resolved by further investigation and scrutiny of methodology, not by appealing to authority or convenience.
Question 3: A headline reads: 'Scientists discover gene linked to intelligence.' A critical reader should first ask:
- Whether the scientists have PhDs in genetics
- What 'linked to' meansāassociation, predictive correlation, or causal mechanismāand how large the effect size is (Correct answer)
- Whether intelligence is a socially desirable trait
- How many countries participated in the study
Correct answer: What 'linked to' meansāassociation, predictive correlation, or causal mechanismāand how large the effect size is
Vague causal language like 'linked to' can mean anything from a weak statistical association to a strong causal mechanism; effect size and mechanism are essential to evaluate the claim.
Question 4: A pharmaceutical trial is stopped early because initial results show the drug is highly effective. Critics warn this could overestimate the drug's benefit. Why?
- Stopping early always indicates ethical violations
- Early stopping biases results upward because trials are more likely to be halted during chance positive fluctuations (Correct answer)
- The drug was never properly tested if the trial ended early
- Early results are always more accurate than long-term results
Correct answer: Early stopping biases results upward because trials are more likely to be halted during chance positive fluctuations
Trials stopped at an unusually positive moment tend to capture a peak in natural statistical variation, causing the true effect to be overestimated relative to what a full trial would show.
Question 5: A study finds that teenagers who play violent video games are more aggressive. The researchers controlled for prior aggression levels, age, and gender. A critic argues that more aggressive teenagers may simply prefer violent games. This is an example of:
- The fundamental attribution error
- Reverse causation as an alternative explanation for the observed correlation (Correct answer)
- A selection bias in how researchers recruited participants
- An appeal to nature fallacy
Correct answer: Reverse causation as an alternative explanation for the observed correlation
Reverse causation suggests the effect (aggression) precedes and causes the exposure (game choice) rather than the other way around, which the study design cannot rule out.
Question 6: A scientist proposes that meteor impacts caused mass extinctions. She points to a global iridium layer coinciding with the Cretaceous-Paleogene boundary as evidence. Iridium is rare on Earth but common in meteors. This evidence is best described as:
- Conclusive proof that a meteor caused the extinction
- Consistent with the hypothesis and would be expected if a large meteor struck Earth, lending support without being definitive alone (Correct answer)
- Irrelevant because iridium cannot survive a meteor impact
- Sufficient to falsify the competing volcanic hypothesis entirely
Correct answer: Consistent with the hypothesis and would be expected if a large meteor struck Earth, lending support without being definitive alone
The iridium layer is a predicted observable consequence of a meteor impact, making it consistent evidence that supports but does not alone confirm the hypothesis.
Question 7: A government agency claims a new pesticide is safe because it has not been banned. A toxicologist responds that absence of a ban does not equal proven safety. Which principle does the toxicologist invoke?
- The precautionary principle, distinguishing between lack of evidence of harm and evidence of lack of harm (Correct answer)
- The principle of regulatory supremacy over scientific evidence
- Occam's razor applied to risk assessment
- The null hypothesis that all chemicals are harmful
Correct answer: The precautionary principle, distinguishing between lack of evidence of harm and evidence of lack of harm
The toxicologist correctly distinguishes between no evidence of harm (the regulatory status) and positive evidence of safety, which requires active testing.
LNAT Science 5
A passage describes an experiment where rats given high doses of artificial sweetener developed tumours.
The author concludes the sweetener is dangerous for humans.
What is the primary weakness of this conclusion?