DISTRIBUTIONSCORE

Poisson Arrivals

Counts of rare independent events per window: calls, mutations, clicks.

λ mean ≈ variance
counts per window · recreated schematic

How it works

  • Events arrive independently at a steady average rate λ.
  • Variance equals the mean — one parameter does everything.
  • Windows scale cleanly: double the time, double λ.
Use → Staffing, queues, buffers. Don't use when events cluster or cascade.
Watch out → Bursts, schedules, or contagion violate independence — reach for negative-binomial instead.
Try it → Count support tickets per hour for a week; compare mean vs variance.
REDCAPE jobs → Predict · Design
Free sources → OpenIntro Statistics (CC BY-SA) • Wikipedia: Poisson distribution (CC BY-SA)