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Phase 11

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.
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    Visual Workflows

    What is LLM Evaluation?

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    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.

    LLM Evaluation
    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 debugging

    Commands to Remember

    Commands to Remember

    • pip install langsmith # trace and evaluate LLM runs
    • pip install arize-phoenix # open-source LLM observability
    • pip 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