2.3 — Zero-Shot, Few-Shot, and Chain-of-Thought

CCAR-P Domain 2 · Task 2.3

What You Need to Know

Escalation Ladder (cheapest first)

1. Zero-shot with clear instructions — baseline; covers most production tasks
2. Few-shot examples — 3–5 relevant, diverse, structured (XML tags)
3. Chain-of-thought / built-in thinking — multi-step reasoning only

Diagnose before adding anything. Instruction quality is the first, free fix.

Matching Technique to Failure

Failure symptom	Cheapest effective fix
Output format wrong/drifting	Few-shot with exact-format example
Inconsistent classification at boundaries	Few-shot with boundary examples
Wrong answers on multi-step reasoning	CoT or built-in thinking
Stated rules ignored	Instruction clarity & structure first
Any of the above	Never a model upgrade first

Few-Shot Properties

Relevant, diverse (edge/boundary cases), structured. Inflate every request unless in cached static prefix.

CoT / Built-in Thinking

CoT buys accuracy on multi-step reasoning; adds latency/tokens. Separate reasoning from final answer with tags. Current models have adaptive thinking (always on for Fable/Opus; default on for Sonnet/Haiku). Prompted CoT remains portable and auditable where needed.

Exam Traps

• Responding to prompt-shaped failures by moving to a larger model
• Offering CoT for a format-compliance failure
• Offering few-shot for a multi-step reasoning failure
• Enabling CoT without separating reasoning from the final answer