Classification
Identify groups, categories, and odd patterns
Classification questions ask you to identify the common rule shared by a group of items and find the item or group that does not belong. The rule may be numerical, algebraic, verbal, structural or based on category membership. A good solution states one precise property, checks it against every option and avoids relying on an unstated convention.
Key formulas and rules
4 rulesOdd-one-out rule = a property shared by the matching items + one clear exception.
Numerical checks: tests evenness and tests whether n is a perfect square.
A category is useful only when the same defining property applies at the same level to every matching item.
Best classification = simplest rule that explains all matching options and isolates one option without exceptions.
Key concepts
What a classification question tests
The task is to find a defining property, not merely a similarity. In an odd-one-out question, three choices may share a category while one does not. In a group question, each option may contain several items and one group may violate the common rule. State the rule in one short sentence before choosing.
Numerical properties
Check parity, primality, divisibility, factors, perfect squares or cubes, digit patterns and arithmetic relationships. Test the property on every number, including the apparently obvious ones. For example, one composite number inside a group of primes is enough to classify that group as different.