Play it: https://craftkeg.github.io/split-decision/
A single-page browser game that teaches the difference between fixed-time and anytime-valid statistical inference — staged inside the November 2024 Tyson vs. Paul broadcast at AT&T Stadium.
You are the PM on call for a Netflix-scale launch. Eight rounds, ten seconds each, seven release cells. One cell has a real regression hiding in the noise. Find it before the bell. Pick wrong and you ship a false alarm. Pick nothing and the broken cell ships live.
Pick a corner before the opening bell:
- Red Corner — Fixed-Time. Sharp Wilson/Newcombe intervals. Every peek is another shot at being fooled by noise.
- Blue Corner — Anytime-Valid. Confidence sequences. Wider bands, but they stay valid every time you look.
Hosted: https://craftkeg.github.io/split-decision/
Or open index.html directly in any modern browser. No build step, no dependencies — one HTML file with inline CSS/JS.
| Outcome | Score | Counter |
|---|---|---|
| Click the real broken cell | +1 | "Caught" |
| Click any other cell | −1 | "FA" (false alarm) |
| Don't pick before the bell | −1 | "Miss" (timeline shows a grey dot) |
The pill labelled R x/8 shows your round, with FIXED-TIME or ANYTIME-VALID next to it indicating which corner you chose.
Both corners compare two arms of streaming traffic per cell at α = 0.10.
Fixed-time corner uses the Newcombe hybrid-Wilson interval for a difference of proportions:
CI = [pT_lo − pC_hi, pT_hi − pC_lo]
where pT_* and pC_* are 90% Wilson bounds on each arm.
Anytime-valid corner uses the asymptotic e-process radius from Lindon (2022):
z_AV(g, n, α) = √( (g + n) / n · ln( (g + n) / (g · α²) ) )
CI = (p̂T − p̂C) ± z_AV · √( p̂T(1−p̂T)/nT + p̂C(1−p̂C)/nC )
with g = 1, n = nT + nC. This is a confidence sequence: it is valid at every sample size simultaneously, not just at a pre-specified one. The cost is wider intervals (≈2× at typical sample sizes), the benefit is that "peeking" no longer inflates the false-positive rate.
Both methods are computed live every frame so you can watch the intervals contract as the round plays out.
- Travis Brooks — for the framing that turned this into a PM monitoring a live event rather than an abstract A/B exercise.
- Matthew Wardrop and Michael Lindon — for feedback that shaped the gameplay and statistical framing.
The anytime-valid radius is a JS port of z_radius from the avlm R package by Michael Lindon, which implements the methodology from:
Lindon, M. (2022). Anytime-Valid Linear Regression. arXiv:2210.08589 — https://arxiv.org/abs/2210.08589
avlm is MIT-licensed.
Commentary lines are stylised dramatisations of the actual Netflix broadcast (Mauro Ranallo, Andre Ward, Rosie Perez, Jessica McCaskill).
MIT — see LICENSE.