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Q&A How does Pr(an event next year) $= 1/100$ imply Pr(at least one of these events occurring in the next 25 years) $> 1/5$?

posted 3y ago by Nat‭

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#1: Initial revision by $user avatar$ Nat‭ · 2021-06-10T23:13:26Z (over 3 years ago)

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**_tldr_&ndash;**  It's a persuasive-writing issue, not a math issue.

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If an event has a 1% chance per year, then it has a ${ \left( 1 - 0.01 \right) }^{25} \approx 0.7778 ,$ or ~77.78%, chance of not happening in 25 years, and so a ~22.22% chance of happening at least once in those 25 years.

That's more than one-in-five.

The author seems to argue that such a statistic might be more compelling to an irrational reader (given the book's title).

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