Learn AI in Bits podcast

091 - How Do We Test AI? Benchmarks and Evals Explained

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AI models get ranked constantly on benchmarks, but what do those scores tell you about whether a system will work in the application you're building? This episode separates two distinct ideas: benchmarks, which compare models on standardized tasks, and evals, which test whether a specific AI system meets its own requirements.


A benchmark gives different models the same set of questions and compares results, like an exam that lets you compare students on the same paper. MMLU covers broad academic knowledge, GPQA tests graduate-level science questions designed to challenge experts in the field, and Stanford's HELM project evaluates models across many scenarios using seven metrics beyond accuracy, including efficiency, bias, and toxicity. The episode is direct about benchmark limits: a model can score well and still fail at a specific job, especially if the test doesn't reflect the users, data, or consequences of a mistake that your application faces, or if models have effectively memorized similar questions during training.


That's where evals come in, built around a specific task instead of general capability. The episode works through a sample eval for a customer-support chatbot: one test case checking a correct return-policy answer, a harder case checking the bot doesn't cave to a customer pushing past the policy window, and a third checking it refuses to leak another customer's private order details. Re-running a small, fixed eval set like this after every prompt, model, or code change is what catches a regression — like a new version inventing refund promises or exposing data — before customers do. The episode covers how to grade results: some outcomes are checked automatically, others need human reviewers or a model-based judge, which should itself be calibrated against human ratings since AI judges carry their own biases, such as favoring longer answers.


For agents specifically, the episode points to METR's research measuring how long and complex a task frontier AI agents can complete reliably on software and engineering tasks with clear success criteria, a very different measurement from a multiple-choice test. The takeaway: benchmarks tell you how a model performs on a shared test, but your own evals, built around your own users' requests and edge cases, are what protect them.


Sources & References

OpenAI: Evaluation best practices — https://developers.openai.com/api/docs/guides/evaluation-best-practices

OpenAI: Working with evals — https://developers.openai.com/api/docs/guides/evals

Stanford Center for Research on Foundation Models: HELM: Holistic Evaluation of Language Models — https://crfm.stanford.edu/helm/

Stanford CRFM: HELM Capabilities — https://crfm.stanford.edu/helm/capabilities/latest/

METR: Task-Completion Time Horizons of Frontier AI Models — https://metr.org/time-horizons/

METR: Time Horizon 1.1 methodology — https://metr.org/blog/2026-01-29-time-horizon-1-1/


Voice narration is AI-generated.

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