Deductive and Inductive Reasoning Flashcards

An investigator argues: 'All criminals lie. John lied to police. Therefore, John is a criminal.' What is the flaw in this reasoning?

Answer: Lying does not make someone a criminal; the conclusion does not follow from the premises

This commits the fallacy of affirming the consequent—many non-criminals also lie, so lying alone does not establish criminality.

Drug seizures at Port A increased significantly after K9 units were deployed. Port B has similar traffic volume and layout. What does inductive reasoning suggest about deploying K9 units at Port B?

Answer: K9 units are likely to increase seizures at Port B as well

Analogical inductive reasoning uses similar conditions to predict probable outcomes, though identical results are not guaranteed.

An investigator states: 'We've seen 40 cases where a clear motive preceded the crime, so motive probably preceded this crime too.' This is an example of which type of reasoning?

Answer: Inductive reasoning

Drawing a probable general conclusion from a collection of specific observed cases is the hallmark of inductive reasoning.

If the alarm was triggered, security was notified. If security was notified, the footage was reviewed. The footage was NOT reviewed. What can be concluded?

Answer: The alarm was not triggered

Applying the contrapositive through each step: no footage review means security was not notified, which means the alarm was not triggered.

A suspect's alibi is confirmed by a single witness who has a prior conviction for perjury. What is the most reasonable investigative conclusion?

Answer: The alibi requires corroboration from additional independent sources

A single witness with credibility concerns does not confirm or disprove the alibi; additional corroboration is needed.

Every car involved in the hit-and-run was either red or blue. No blue cars were found in the area. A red car was found three blocks away. What can be concluded?

Answer: The red car is a candidate for involvement and warrants investigation

Eliminating blue narrows the field to red vehicles, making the nearby red car a candidate, but physical confirmation is still required.

The rule 'No unauthorized person may enter the evidence room' is logically equivalent to which of the following statements?

Answer: Only authorized persons may enter the evidence room

Saying no unauthorized person may enter is logically equivalent to saying access is restricted to authorized persons only.