LNAT Science 3 — Questions and Answers
Question 1: A passage states that a vaccine prevents disease in 95% of recipients. A critic argues this means 5% of vaccinated people will get the disease. Which response best challenges the critic's interpretation?
- The critic correctly understands vaccine efficacy statistics
- The 95% figure is an efficacy rate comparing vaccinated to unvaccinated groups, not an absolute guarantee for individuals (Correct answer)
- Vaccines never cause any adverse effects so the critic is wrong on all counts
- The 5% failure rate is acceptable and the critic should not raise it
Correct answer: The 95% figure is an efficacy rate comparing vaccinated to unvaccinated groups, not an absolute guarantee for individuals
Vaccine efficacy compares disease rates between vaccinated and unvaccinated groups; a 95% rate means the vaccine reduces risk by 95%, not that 5% of recipients are guaranteed to contract the disease.
Question 2: Scientists observe that species diversity is lower near industrial sites. They hypothesize that pollution causes biodiversity loss. Which additional evidence would best support this hypothesis?
- Historical records showing biodiversity was higher in the area before industrialization (Correct answer)
- A survey of public attitudes toward local wildlife
- Data showing that similar industrial sites exist in other countries
- A report that the companies operating the sites are profitable
Correct answer: Historical records showing biodiversity was higher in the area before industrialization
Historical baseline data showing higher diversity before industrialization establishes a temporal link consistent with the pollution hypothesis.
Question 3: A study measures pain relief in patients using either acupuncture or sham acupuncture (needles placed at incorrect points). Both groups report similar improvements. The most defensible conclusion is:
- Acupuncture is the most effective pain treatment available
- The improvement in both groups is likely due to a placebo effect rather than needle placement (Correct answer)
- Sham acupuncture is more effective than real acupuncture
- The study is worthless because it used an unethical control group
Correct answer: The improvement in both groups is likely due to a placebo effect rather than needle placement
When real and sham treatments produce equal results, the most parsimonious explanation is that expectation (placebo) rather than the specific intervention is driving the effect.
Question 4: A government report claims CO₂ emissions fell by 10% last year. A scientist notes that industrial output also fell by 12% due to an economic recession. What does this suggest about the emissions data?
- The 10% reduction proves environmental policy was successful
- The reduction may be explained by lower economic activity rather than policy changes (Correct answer)
- CO₂ emissions are unrelated to industrial production
- The scientist is attempting to undermine environmental protection
Correct answer: The reduction may be explained by lower economic activity rather than policy changes
A confounding economic factor (reduced production) can explain the emissions drop without crediting environmental policy.
Question 5: A researcher observes that students who sleep more than 8 hours score higher on cognitive tests. She publishes a paper titled 'Sleep Improves Cognition.' Which limitation is most significant?
- The study did not measure sleep quality, only duration
- The direction of causality is unclear; higher cognitive ability may lead to better sleep habits (Correct answer)
- The sample should have included older adults
- Cognitive tests are not reliable measures of intelligence
Correct answer: The direction of causality is unclear; higher cognitive ability may lead to better sleep habits
Observational data cannot establish which direction causality runs; it is equally plausible that cognitively healthier individuals happen to sleep more.
Question 6: An argument reads: 'Science cannot explain consciousness, therefore consciousness must be non-physical.' This argument commits which logical error?
- Circular reasoning
- An argument from ignorance, assuming unexplained implies inexplicable or non-physical (Correct answer)
- A false dichotomy between science and philosophy
- Ad hominem against neuroscientists
Correct answer: An argument from ignorance, assuming unexplained implies inexplicable or non-physical
The argument from ignorance (argumentum ad ignorantiam) incorrectly treats current scientific limitation as proof of a positive metaphysical claim.
Question 7: A nutritional study followed 10,000 people for 20 years and found that daily coffee drinkers had lower rates of Type 2 diabetes. The researchers controlled for BMI, exercise, and smoking. What type of study is this and what can it conclude?
- A randomized controlled trial that proves coffee prevents diabetes
- A large observational cohort study that shows an association but cannot establish causation (Correct answer)
- A case-control study that definitively rules out confounding variables
- An experimental study that directly tests coffee's biochemical effect
Correct answer: A large observational cohort study that shows an association but cannot establish causation
Following participants over time without intervention makes this a cohort study, which can identify associations but cannot prove causation even with controls.
LNAT Science 3
A passage states that a vaccine prevents disease in 95% of recipients.
A critic argues this means 5% of vaccinated people will get the disease.
Which response best challenges the critic's interpretation?