Confidence Strings, Not Scores: Why Your 0.87 Badge Moves Nobody
The product team ships a confidence badge next to every AI suggestion. Green for ≥85%, yellow for 60–84%, red below. They run an A/B test six weeks later and find no change in user behavior at any threshold. False positives at 0.92 confidence get accepted at the same rate as false positives at 0.61 confidence. The team's instinct is to tune the calibration — fit a temperature scaling layer, regenerate the badges, run the A/B again. The numbers shift; the behavior doesn't.
The problem isn't that the model is miscalibrated, though it almost certainly is. The problem is that calibrated probability is the wrong output. The signal a user can act on isn't "how sure" the model is. It's "what specifically the model didn't check." A 0.87 badge tells the user nothing they can verify. "I'm reasonably confident in the address but I haven't checked the unit number" tells them exactly where to look.
