RAG Formation · Reference

Refusal, uncertainty, and hallucination control

A standalone cheat sheet for learning and testing RAG quality on this site.

$ reference --status
▸ course RAG Formation
▸ mode standalone reference
▸ status Complete
● learn → test → verify

Reference sheet

The guided RAG Formation course content is complete; this reference is available for self-directed practice.

One-line rule

A fluent partial answer can still hallucinate if it adds an important claim the evidence does not support.

Term	Meaning
Refusal	A clear statement that the indexed evidence does not establish the requested fact.
Uncertainty	A calibrated explanation of what the evidence supports and what remains unknown.
Hallucination	An important claim presented without enough support from the allowed evidence.

Need	Record	Don't claim
Baseline	Command, configuration, observed result	The baseline is a target.
Change	One hypothesis or decision	You can tell what caused the result when several things changed.
Metric	Track refusal accuracy and hallucination rate separately, plus one answer that crossed the boundary.	One metric tells you everything about quality.
Safety	A failure and a regression case	A fluent answer proves the system is reliable.

cd demo
python3 eval.py run --mode answer --workspace meridian_demo --category unanswerable --tag lesson-12-refusal

Artifact: A refusal policy with test cases for no evidence, partial evidence, conflict, and ambiguity.

Continue learning: Open the matching standalone lesson · Course roadmap