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EvaluationHard· Evaluation & Production

Your offline metrics improved but the online numbers di...

Because offline evaluation measures the model; online outcomes measure the whole system, including the humans using it. Those are different things, and a gap between them is common enough that it should always be an expected possibility, not a surprise.

The usual causes, roughly in order of how often I’ve seen each:

  • Distribution shift — the offline evaluation set no longer resembles live traffic.
  • The wrong metric — the number that improved isn’t actually the thing users care about.
  • A trust or UX problem — the model got measurably more correct, but users don’t act on the output even when it’s right, because the interface doesn’t give them a reason to trust it.

The fix is to instrument human behavior directly — acceptance rate, override rate, edit rate, escalation rate, abandonment — because those measure trust, and trust is ultimately what determines whether the system survives contact with real users, independent of how good the model itself has gotten.

Code playground (Python)