Analogy and Classification test your ability to recognize fundamental relationships, logical similarities, and underlying rules among words, numbers, letters, or shapes, as well as identifying the "odd one out" that violates a common group rule.

1. Analogy Concepts

An analogy statement is expressed in the format $A : B :: C : D$, which reads: "$A$ is to $B$ as $C$ is to $D$". The relationship connecting $A$ and $B$ must be exactly replicated between $C$ and $D$.

Types of Analogy:

• Word / Semantic Analogy: Based on general knowledge, synonyms, antonyms, cause-effect, tool-action, country-capital, or worker-product relationships (e.g., Doctor : Hospital :: Teacher : School).
• Number Analogy: Based on arithmetic operations, squares ($n^2$), cubes ($n^3$), prime numbers, or digit operations (e.g., $5 : 25 :: 7 : 49$).
• Letter / Alphabet Analogy: Based on positional shifts ($+n / -n$), reverse alphabetical order, or opposite letter pairs (e.g., CAT : DDY :: DOG : EQJ).

2. Classification (Odd One Out) Concepts

Classification involves examining a given set of four or five options, identifying a common property or rule shared by all items except one, and picking the item that does not belong to the group.

Types of Classification:

• Word Classification: Grouping by category (e.g., Mammals vs. Reptiles, Metals vs. Non-metals, Continents vs. Countries).
• Number Classification: Grouping by mathematical properties (e.g., Prime numbers vs. Composite numbers, Even vs. Odd, Multiples, Squares / Cubes).
• Letter Classification: Grouping by vowel count, position differences between consecutive letters, or reverse letter pairs.

Key Relationship Types to Remember

• Synonyms / Antonyms: Huge : Gigantic :: Tiny : Small.
• Worker & Tool: Carpenter : Saw :: Author : Pen.
• Tool & Action: Knife : Cut :: Microscope : Magnify.
• Quantity & Unit: Current : Ampere :: Power : Watt.
• Animal & Young One: Dog : Puppy :: Lion : Cub.
• Number Operations: $x : x^2 + 1$, $x : x^3 - 1$, or ratio multipliers.

A reliable step-by-step approach

1. For Analogy ($A : B :: C : ?$), formulate a precise sentence stating how $A$ relates to $B$.
2. Apply that exact sentence to $C$ to find $D$. Ensure the direction of relationship remains consistent ($A \to B$ vs $B \to A$).
3. For Classification, find a positive rule that connects 3 (or 4) options together, rather than just pointing out why 1 option looks different.
4. If numbers are involved, test basic arithmetic, prime status, and square/cube relations before looking at digit sums.
5. For letter patterns, write down positional numbers ($1$ to $26$) to detect constant or incremental shifts.

Common mistakes

• Reversing the order of relationship (e.g., matching Cause : Effect with Effect : Cause).
• Choosing an odd-one-out based on superficial traits without finding a unifying rule for the remaining choices.
• Relying on rare or obscure word meanings when a direct category relationship exists.
• Forgetting that prime numbers take priority over odd/even classifications in number sets.

Quick revision summary

• Analogy rule: Relationship between 1st & 2nd terms = Relationship between 3rd & 4th terms.
• Classification rule: Identify the common feature shared by majority items first.
• Always check Primes $\to$ Squares/Cubes $\to$ Multiples $\to$ Digit Sum in number questions.