LLM Evaluation
~2 min read
Concept & How It Works
Why Does It Exist?
Prompt and model changes have unpredictable effects. Systematic eval prevents shipping regressions and quantifies improvements for stakeholders.
Real-World Analogy
LLM eval is standardized testing for models — same questions, scored rubrics, comparable grades across versions.
Visual Workflows
What is LLM Evaluation?
Example
Scenario
Eval set of 200 FAQ pairs; new model scores 87% exact match vs 91% baseline — investigate 26 regressions before release.
Solution
In Agent Evaluation & Observability, apply LLM Evaluation to this scenario: Eval set of 200 FAQ pairs; new model scores 87% exact match vs 91% baseline — investigate 26 regressions before release. Identify the inputs, run the technique, validate the output, and note one thing you would monitor in production.
Practice Task
Do this before moving to the next module — reading alone is not enough.
Open the Code Walkthrough below and run it locally. Change one parameter related to LLM Evaluation (e.g. model, temperature, top_k, or tool name), observe the difference in output, and write 2–3 sentences explaining what changed.
Code Walkthrough
Highlighted lines show where LLM Evaluation happens in the code.
1def exact_match(pred, ref): # define a reusable function2 return pred.strip().lower() == ref.strip().lower() # return the result3
4scores = [exact_match(agent(q), ref) for q, ref in eval_set]5print(f"EM: {sum(scores)/len(scores):.1%}") # show output for debuggingCommands to Remember
Commands to Remember
pip install langsmith # trace and evaluate LLM runspip install arize-phoenix # open-source LLM observabilitypip install opentelemetry-api opentelemetry-sdk # distributed tracing
Common Mistakes
- Treating LLM Evaluation as a black box without evaluation
- Ignoring cost and latency in production
- Skipping error handling for llm evaluation
Cheat Sheet
Quick recap — the most important points from this module.
Cheat Sheet
quick ref- •LLM Evaluation
- •LLM-as-Judge
- •Golden Set
- •pass@k