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ToraToraTora | 10:15 Thu 05th Jan 2023 | ChatterBank
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in a room of 23 people there is a 50% chance that 2 of them share the same birthday (month and day)?
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carrot99, it does not work like that. What you have to do is, starting with one person, work out the probability that another person does not have the same birthday (364/365) and then keep adding people, calculating the probabilities and multiplying them. Your calculation should be (364/365)x(363/365)x(362/365)x... etc. When this product drops below...
10:37 Thu 05th Jan 2023
some twins don't even share a birthplace

https://www.bbc.co.uk/newsround/35350306

carrot, if you had 32 days that would be a 100% chance of two of them being born on the same day. For a 50% chance you'd need fewer.
what you are calculating is the probability that each additional person has a different birthday from all those already present. Once this drops to less than 0.5, it means that it is more than 50% likely that two people do share the same birthday
carrott - it's terminology. A probability of 0.5 is the same as a 50% chance. A probability of 1 is 100% chance, a probability of zero is 0% chance.
Thank you again nescio and thank you jno.
in fact as soon as there were 367 people in the room there will be 100% chance that two will celebrate the anniversary of their birth on the same day
Johnny - that's what I said at 11:06.
yes, because the probability that the 366th or 367th person does not share a birthday with anyone else is now 0/365 (or 0/366) - there are no possibilities left - so the overall product becomes zero.
When I was a youngster at home, with 4 people in a room there was a 100% chance of 2 of them sharing the same birthday (hour, day, month,year).
Oh heaven's canary, does that mean you have a twin.... Or was it two others.
// 100% chance of 2 of them sharing the same birthday (hour, day, month,year) //

And conversely, 0% chance (min, hour, day, month, year).



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