Live demo
13 series in. 4 alerts out.
One paid social account, 60 days, 13 series across four creative assets. On day 42 the engagement rate on hook-a-summer-v3 breaks. Its click-through follows two days later and its conversion metrics only move on day 48. Account-level CPA, spend, and impressions never turn. Find the asset and the date.
Every number on this page is computed in your browser right now, by the same CUSUM and Bayesian changepoint code that runs in production. Nothing here is a screenshot.
The comparison that matters
Against the rule most teams actually ship
The standard configuration is a percentage or sigma threshold against a trailing mean, evaluated per metric. Run it over the exact same 13 series and count what lands in the channel.
The false-alarm count is not a judgement call. The incident was injected at a known index, so every naive alert before that index is wrong by construction.
What the engine found
Detection run
| Metric | Trend | Baseline | Now | Change | Confidence | Method |
|---|---|---|---|---|---|---|
Engagement rate creative=hook-a-summer-v3 | 3.85% | 2.20% | −42.7% | 99.9% | CUSUM | |
Click-through rate creative=hook-a-summer-v3 | 1.44% | 0.90% | −37.6% | 99.9% | CUSUM | |
Cost per acquisition creative=hook-a-summer-v3 | $41 | $72 | +73.7% | 99.9% | CUSUM | |
Conversion rate creative=hook-a-summer-v3 | 2.93% | 1.88% | −35.9% | 99.9% | CUSUM |
Show your work
Engagement rate · creative=hook-a-summer-v3
Baseline mean μ = -0.0002 and σ = 0.0452, both computed from the first two thirds of the day-over-day percentage changes. The slack k = 0.0226 is half a sigma, and the decision boundary h = 0.1810 is four. The accumulator runs on percentage changes rather than raw levels so a healthy growing series cannot drift across the boundary on its own.
alert if |Δ| > 3σ vs 7-day mean fired 3 times across this one metric, including 1 before anything was actually wrong. The statistical pipeline sent one message, on the day the regime actually changed.
What lands in Slack
One message, with the work already done
- 1.Cap frequency on hook-a-summer-v3 or rotate it out; it has been past its useful life since Aug 10.
- 2.Move its budget to carousel-offer-v4, whose click-through has held flat at 1.5% across the whole 60-day window.
- 3.Re-cut the hook rather than the offer. Engagement broke before conversion, which points at the first three seconds, not the landing page.
The written cause is generated only after the statistics confirm the change. The model never decides whether something is an anomaly — it explains one that has already been established. Getting that order backwards is how these products hallucinate.