CCTST Inference 5 — Questions and Answers
Question 1: A scientist observes that every swan seen over 200 years has been white. Which inference is most logically sound?
- All swans that exist anywhere are white.
- All swans observed so far in this dataset have been white. (Correct answer)
- There are no black swans anywhere in the world.
- Swans evolved to be white for survival purposes.
Correct answer: All swans observed so far in this dataset have been white.
Inductive generalizations from observation are limited to the evidence gathered; they do not guarantee universal truth.
Question 2: An insurance company charges higher premiums to drivers under 25. This practice is most likely based on what kind of inference?
- Young drivers are reckless by nature.
- Statistical data show higher accident rates for drivers under 25. (Correct answer)
- Young people cannot afford higher premiums.
- Older cars driven by young people are less safe.
Correct answer: Statistical data show higher accident rates for drivers under 25.
Actuarial pricing relies on statistical group patterns rather than assumptions about any individual driver's character.
Question 3: A doctor says, 'The X-ray suggests a fracture.' The word 'suggests' indicates:
- The fracture is definitively confirmed.
- The evidence points toward a fracture but is not conclusive. (Correct answer)
- No fracture is present.
- A second opinion is always required by law.
Correct answer: The evidence points toward a fracture but is not conclusive.
Hedging language like 'suggests' signals a probabilistic inference that the evidence supports but does not prove.
Question 4: If the premises 'All fish have gills' and 'Sharks are fish' are both true, the conclusion 'Sharks have gills' is:
- A probable but not certain conclusion.
- A valid deductive inference that must be true if premises are true. (Correct answer)
- An inductive generalization from observation.
- An assumption that requires further study.
Correct answer: A valid deductive inference that must be true if premises are true.
This is a valid syllogism: the conclusion follows necessarily from the two true universal premises.
Question 5: A wine expert tastes a wine and infers it is from a specific region based on its flavor profile. This is an example of:
- Deductive reasoning from explicit rules.
- Inference to the best explanation based on sensory evidence. (Correct answer)
- A wild guess with no logical basis.
- Statistical sampling of wine types.
Correct answer: Inference to the best explanation based on sensory evidence.
The expert draws the most plausible conclusion that explains the observed evidence, a form of abductive reasoning.
Question 6: A survey asks 500 college students about sleep habits and reports results as representing 'all Americans.' This inference is flawed because:
- The sample size is too large.
- College students are not a representative sample of all Americans. (Correct answer)
- Sleep habits do not vary across populations.
- Surveys cannot measure sleep accurately.
Correct answer: College students are not a representative sample of all Americans.
Generalizing from a non-representative sample to a broader population commits the fallacy of hasty generalization.
Question 7: Premises: 'If the power is out, the alarm won't sound. The alarm sounded.' What can be inferred?
- The power was out.
- The power was not out. (Correct answer)
- The alarm is malfunctioning.
- Nothing can be concluded.
Correct answer: The power was not out.
Using modus tollens: if the alarm sounded, the condition that would have prevented it (power outage) did not occur.
CCTST Inference 5
A scientist observes that every swan seen over 200 years has been white.
Which inference is most logically sound?