“Cumulative Sums of the Poisson” – affectionately called the “Thorndike Chart”

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An old Nomograph that can save Risk Analysts and Reliability Engineers a lot of time: “Cumulative Sums of the Poisson” – affectionately called the “Thorndike Chart”

If you ever had to explain to a customer that the expected number of “catastrophic” events over the next (say) 10 years is a small fraction < 1. ..(say 0.26 events).. Using the Thorndike chart you can see that using µ=0.26, the Probability of seeing 1 (or more) events over the same time period is 0.24. Much easier to explain to a customer than 0.26 “expected” events!! Thorndike Chart

Previously published in the June 2013 Volume 4, Issue 2 ASQ Reliability Division Newsletter

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The following special course is presented by ASQ’s Reliability and Risk Division at RAMS 2022. Registration linkSunday course canceledThursday,January 27, 2022andFriday,January 28, 2022Communicating Reliability, Risk, and Resiliency to Decision MakersJanuary 27, 2022, 1:00 p.m. – 5:00 p.m.and January 28, 2022, 8:00 a.m. – noonSonoran conference room at the El Conquistador Resort Getting your boss’s boss to understand is one

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