The birthday paradox and how does it work on this board?

[Sporting]

https://betterexplained.com/articles...thday-paradox/

If 23 of us post then there's evidently a 50% chance of two of us sharing a birthday.

I was born on June 6th.

[Janik]

Given that Football squads for international tournaments have settled realtively recently at 23 players, they form the perfect example data set of this 'paradox' (the wrong word, surely? There is nothing paradoxical about this particular statistical fact). For example, the squads at last year's Women's World Cup:- https://en.m.wikipedia.org/wiki/2019...rld_Cup_squads

[Janik]

And on why this boggles the mind - humans have a tendency to self-centre on hypotheticals like this. We tend to think of the situation as if there is a group of 23 and I'm part of it, then there is a 50% chance of someone sharing a birthday with me. But that isn't what is being said. It's any pair out of the 23. If you are part of the group, its much more likely to be two others who share the birthday.
There are lots of possible pairs when you have that many individuals. 253 unique combinations, in fact. And when looked at like that, well, it's not much of a surprise that one of these unique combinations will share a random attribute which has a 1-in-365 chance.

[johnr]

I showed that this normally works at a couple of parties a few years ago (I'm a fun kind of guy) and won a fiver each time, to the astonishment of the people there.

[pebblethefish]

My birthday is 25 November. No one else is allowed that birthday. If it's yours already, fuck off. Change it. That day is all about me.

[Janik]

Oh, and I'm not posting my birthday up online for this purpose. Sensitive personnel information and all that. I only input it when it's absolutely neccesary.

[Evariste Euler Gauss]

What Janik said. Sorry to be pedantic, but it's not really a "paradox". It's just a mathematical fact for which our intuition is not well-attuned.

[Sporting]

I should have used inverted commas.

[Sporting]

Oh, and I'm not posting my birthday up online for this purpose. Sensitive personnel information and all that. I only input it when it's absolutely neccesary.

That's cool; I completely understand.

[pebblethefish]

Oh, and I'm not posting my birthday up online for this purpose. Sensitive personnel information and all that. I only input it when it's absolutely neccesary.

We can already tell from that post that you're clearly a Libra

[Rogin the Armchair fan]

I share my birthday with Jose Mourinho. Does he post on here?

[Kevin S]

I know that I share mine with another poster fwiw.

[Jah Womble]

You lot count yourselves lucky - I had to share mine with my dad.

[Nefertiti2]

You lot count yourselves lucky - I had to share mine with my dad.

That must have been hard for your mum and your 21 siblings.

[Jah Womble]

Ha - just the one sibling. And her birthday falls four days later.

My mother's - obviously - was bang in between.

[Wouter D]

Oh, and I'm not posting my birthday up online for this purpose. Sensitive personnel information and all that. I only input it when it's absolutely neccesary.

We would also be interested to learn your mother's maiden name, the name of your first pet, your childhood nickname...

[DCI Harry Batt]

https://betterexplained.com/articles...thday-paradox/

If 23 of us post then there's evidently a 50% chance of two of us sharing a birthday.

I was born on June 6th.

That link reminded me - when did people start saying "a tad bit"?

[ad hoc]

That link reminded me - when did people start saying "a tad bit"?

Do people say that? Eurgh.

[DCI Harry Batt]

ikr

[3 Colours Red]

Do I need to share my H.P. Lovecraft/Joe Pasquale quip again? It seems I've dragged it out every August the 20th since I joined.

[3 Colours Red]

Oh, and I'm not posting my birthday up online for this purpose. Sensitive personnel information and all that. I only input it when it's absolutely neccesary.

As long as you don't add your first pet's name, your favourite meal and the three digits on the back of your bank card, I think you're fine.

[NHH]

In similar using maths and stuff to win bets, I won a sweepstakes at a wedding for guessing the length of the best man's speech by doing that wisdom of crowds thing where you get the average of all guesses. Works a treat.

[ursus arctos]

Doesn't it require you to go late in the sequence?

[caja-dglh]

Mine is June 6 also.

(it isn't)

[Duncan Gardner]

I generated 10 sets each of 23 random birthdays in the same year. One set had a pair with shared date, another 2 such pairs, and the other 8 none at all