AI article
Base Rate Neglect: Why Your "95% Accurate" Alert Is Wrong 99% of the Time
Community description: Google Flu Trends ran hot in 100 of 108 weeks. Your cost-anomaly alert has the same bug. Here's the Bayes math, and a pre-flight fix in Python.
Dev.to | Oct 3, 2026 | Orvi Das
Automated excerpt
"""P(real incident | alert fired), via Bayes. """ print(precision(1 / 2000, 0. 95, 0. 05)) # 0. 0094 That's under 1%. Ginsberg and colleagues screened 50 million candidate search queries against CDC regional flu data, kept the 45 that fit best, and hit a mean correlation of 0. 90 on validation data. Before you ship any new alert, run it through precision() with an honest base rate.
Selected automatically from source text; not independently written or fact-checked. Read the original for full context.