# Chain-of-Thought (CoT) Prompting

Canonical: https://aimastermindlab.com/glossary/chain-of-thought

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Chain-of-Thought prompting elicits step-by-step reasoning from an LLM before it produces a final answer. By showing or requesting intermediate reasoning steps, CoT dramatically improves accuracy on arithmetic, logical reasoning, and multi-step problem-solving tasks.

## What is Chain-of-Thought Prompting?

Chain-of-Thought (CoT) prompting is a technique that encourages LLMs to produce intermediate reasoning steps before arriving at a final answer. Wei et al. (2022) demonstrated that this simple approach dramatically improved reasoning accuracy on benchmarks like GSM8K and MATH.

## Few-Shot CoT

Provide examples that include reasoning steps:

```
Q: Roger has 5 tennis balls. He buys 2 more cans of 3 balls each. How many tennis balls does he have?
A: Roger starts with 5 balls. 2 cans × 3 balls = 6 balls. 5 + 6 = 11 balls. The answer is 11.

Q: The cafeteria had 23 apples. They used 20 for lunch and bought 6 more. How many apples do they have?
A: [model reasons step by step]
```

## Zero-Shot CoT

Simply append "Let's think step by step" to any question — the model then reasons before answering. This was shown to improve GSM8K accuracy from ~18% to ~79% for certain models.

## When CoT Helps Most

- **Arithmetic reasoning** — Multi-step calculations.
- **Logical deduction** — If-then chains, syllogisms.
- **Planning tasks** — Scheduling, resource allocation.
- **Code debugging** — Tracing execution flow.

CoT provides little benefit for simple tasks (factual lookup, sentiment classification) and adds unnecessary tokens.

## Variants

- **Tree-of-Thought (ToT)** — Explores multiple reasoning branches simultaneously.
- **Self-Consistency** — Sample multiple reasoning chains, take a majority vote.
- **Program-of-Thoughts** — Generate code as the reasoning step, execute it for the answer.

## Example

Without CoT: 'What is 17% tip on a $47.50 bill?' → '$8.07'. With CoT: 'First, 10% of $47.50 = $4.75. Then 7% = $3.33. Together = $8.08.' — the reasoning step catches rounding errors and improves reliability.
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Source: https://aimastermindlab.com/glossary/chain-of-thought — AI Mastermind Lab (https://aimastermindlab.com)