Most deductive reasoning tests are built from a small number of recurring formats, so recognising them on sight saves time. This guide covers the method for each.
Practise the real thing: every format below appears in our free deductive reasoning test, with a worked solution for every question. No sign-up.
How syllogism questions work
Chain the premises together and use only what is stated, nothing more. A syllogism is solved by following the links between the groups, not by checking whether the conclusion sounds sensible.
Take a worked example. All footballers are fit and healthy. All famous sports players are footballers. Which conclusion follows? Work the chain: famous sports players are footballers, and footballers are fit and healthy, so all famous sports players are fit and healthy. That is the only conclusion forced by the premises.
The tempting wrong answers are built from reversals and leaps the premises do not support:
- “All footballers are famous sports people” reverses the second premise. Not given.
- “All fit and healthy people are footballers” reverses the first premise. Not given.
- “All football players are men” introduces a fact, gender, that never appears. Not given.
The habit that catches all three: before you accept a conclusion, point to the premises that force it. If you cannot, it is a distractor.
How conditional (if-then) questions work
Test each option against the rule, and remember that a conditional works in one direction only. “If P then Q” tells you that P guarantees Q. It does not tell you that Q guarantees P.
Two moves are always valid, and two always look valid but are not:
- Valid: given the rule and P, you may conclude Q.
- Valid: given the rule and “not Q”, you may conclude “not P” (the contrapositive).
- Invalid: given the rule and Q, you may not conclude P (affirming the consequent).
- Invalid: given the rule and “not P”, you may not conclude “not Q” (denying the antecedent).
The two invalid moves are the ones examiners bank on, because in everyday language people slide between them without noticing. When a question hinges on a conditional, write the rule down as “P then Q” and check which of the four situations the option describes before you answer.
The cannot-be-concluded trap
When the options include “cannot be concluded”, treat it as the correct answer until the premises rule it out. Most candidates lose these marks by filling gaps with sensible-but-unstated assumptions.
Consider a statistics example. This year 94% of students achieved A to C. Last year 95% did. The school credits its new mentoring scheme.* Which statement is true? The only supportable conclusion is that before last year, fewer than 94% achieved A* to C, because results have been rising. Anything about next year’s results, other schools, or every student’s grade goes beyond the data and must be rejected.
Two rules keep you honest:
- Use only the figures and statements given. A cause the passage asserts is not a cause you can rely on.
- A plausible statement is not a provable one. If you cannot trace a statement back to the text, “cannot be concluded” is your answer.
More on deductive reasoning tests
Go back to the full deductive reasoning tests guide, or try the related logical reasoning and inductive reasoning tests.
