Four tests, two instruments, no survivor
The first instrument alarms on noise and on bookkeeping. The rebuild is robust and blind: it detects a real 30% shift less often than it false-alarms. The marked rows are why nothing is prescribed.
Reference & Evidence
Source: diagnostic-v1-failed.py, 20,000 replications: fires on 49.8, 50.7 and 49.6% of runs across three noise levels, the first drawn here. diagnostic-v2-failed.py, 6,000 replications: a one-off 8% cost reclassification, and a ramped 30% variable-cost shift with a bootstrap interval. Both published as failures at isoglu.com/research/gross-margin-panel/.
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