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Does anyone know what the odds are of experiencing a 1 in 125 year event in a 20 year time span?

I feel like sometimes weather records are given higher significance than they really are in the grand scheme of things. Not saying this is one of them, but just trying to look at things in a balanced way.

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Assuming independent events (a bad assumption no doubt) then you're looking for 1 - the probability that for 20 years straight you don't have the event happening.

- E event happens in given year - N event doesn't happen in given year

Then P(E) = 1/125. Conversely P(N) = 1-1/125.

We're looking for 1-P(NNNNNNNNNNNNNNNNNNNN) = 1 - (1-1/125)^20 = 15%

Though I'm sure someone will tell me how I'm wrong

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