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Two survivors of Brown University attack escaped other school shootings (www.theguardian.com)
submitted 8 months ago by to c/news@lemmy.world
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[–] 20 points 8 months ago (2 children)

There's a similar and related math problem for this:

How many people do you need in a room before 2 of them share a birthday?

The answer is around 50, which is way less than most people expect.

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  • [–] 16 points 8 months ago* (2 children)

    At 50 people is is 97% likely and at 60 people it is 99% likely.

    So not guaranteed, but surprising if nobody shares a birthday.

    https://en.wikipedia.org/wiki/Birthday_problem

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  • [–] 1 point 8 months ago* (last edited 8 months ago) (2 children)

    I think the question is usually frames as "how many people does it take to make it at least 50% likely that two people will share a birthday", or more likely than not etc.

    A guarantee would need 366 people. But most people are satisfied with "more likely than not", "90% chance", or "99% chance".

    EDIT: I meant 367, not 366!

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  • [+] -8 points 8 months ago (3 children)

    366 would not guarantee it. That's not how probability works. You cannot guarantee a shared birthday without selecting people. And not to mention, birthdays aren't evenly distributed.

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  • [–] 3 points 8 months ago (2 children)

    Once you have more people than days in a year it's not about statistics anymore

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  • [–] 8 points 8 months ago (1 child)

    366 people wouldnt guarantee no shared birthdays though. There could still be one leap year baby in that bunch. But what are the odds in that?

    2.6 • 10^-158 , if anyone is curious.

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  • [–] 8 points 8 months ago

    If you assume one mass shooting every three days for the last 15 years, and there being 1700 people "present" for each (within earshot, not necessarily immediately in danger), there are now over 3 million people who have now been present for shootings.

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