Deductive and Inductive Reasoning Questions and Answers

Answer: C

If 'most of the students are obedient', then more than half the students are obedient, so some students are obedient (III) must be true. Since the obedient ones are only most, not all, we cannot say all students are obedient, so II is not claimed. I does not follow, as obedient persons may include non-students. IV says some students are not disobedient, which means some students are obedient, and so follows. So III and IV can be claimed, and the answer is III and IV.

Answer: A

A deductive argument claims that its conclusion follows necessarily from its premises. So the conclusion does not go beyond what is contained in the premises (I), and the premises support it conclusively (II). Statement III is false: if the conclusion of a valid deductive argument is false, at least one premise must be false, so the premises cannot be either true or false. Because III is false, the options containing it, 'I and III', 'II and III' and 'all the above', cannot be right. The answer is I and II.

Answer: C

Reasoning by analogy infers that two things which are alike in some respects are alike in a further respect. The conclusion goes beyond the premises, and so it is probable and not certain, which makes it a predictive conjecture. Certainty, a definite conclusion and surety are words for deductive reasoning, in which the conclusion follows necessarily from the premises, and analogy is a form of inductive reasoning. The answer is predictive conjecture.

Answer: C

When the conclusion of an argument follows from its premise or premises conclusively, the argument is called deductive. In a valid deductive argument the truth of the premises guarantees the truth of the conclusion.

An inductive argument only makes the conclusion probable, an analogical argument reasons from likeness between cases and also gives only probability, and a circular argument assumes the conclusion in its premises.

The test of a deductive argument is validity: it is impossible for the premises to be true and the conclusion false, which is the sense of following conclusively.

Answer: C

The argument is analogical. It argues that because Saturn and Mars resemble the earth in being planets that borrow light from the Sun and move around it, they must resemble the earth in being inhabited too.

It is not deductive, since the conclusion does not follow with certainty. It is neither astrological nor mathematical, as it does not use the influence of the stars or any calculation, but only a comparison between similar cases.

Answer: B

If 'some men are honest' is false, then (ii), (iii) and (iv) are true.

The statement is a particular affirmative (I). It is false when its contradictory, the universal negative 'no men are honest', is true, which is (ii). Since no men are honest, some men are certainly not honest, which is (iii), and all men are dishonest, which is (iv).

Statement (i), 'all men are honest', would make 'some men are honest' true, so it cannot hold. Codes that contain (i) are therefore wrong.

Answer: B

The correct statements are (i), (ii) and (iv).

A Venn diagram is a clear notation, it is the most direct way to test the validity of a categorical syllogism, and for a syllogism with three terms three overlapping circles are drawn.

Statement (iii) is incorrect. Only the premises are diagrammed. The conclusion is not drawn but is read from the diagram, to see whether the premises already contain it. Codes that include (iii) are therefore wrong.

Answer: C

Inductive reasoning presupposes uniformity in human nature.

Induction moves from observed cases to a general conclusion. This is justified only if what holds in the cases observed holds in the cases not observed, which assumes that nature, including human nature, behaves uniformly.

Unity, integrity and harmony are not the assumptions that make the leap from observed to unobserved cases acceptable.

The assumption is why induction gives probable and not certain conclusions: a single exception in the unobserved cases can still overturn a general statement.