Abstract
Binary decision aids, that is, indicators that reduce a graded measurement to a category or a bit before an operator sees it, appear across safety-critical engineering. Radiation-therapy interlocks, reactor status lights, cockpit stall warnings, and combat identification systems all share this pattern. They also share a failure mode near the threshold, that is, the regime where the reduction discards the information a rational decision-maker needs to act. This paper treats the problem as one of information loss under quantization, examines four well-documented incidents as illustrative evidence, and argues for a design rule, that is, where a graded measurement is available, carry the confidence forward and present it alongside the decision rather than only the argmax. The four incidents help illustrate the argument; they do not attempt to prove it in a statistical sense.