A probability problem... probably.

[amnesia]

According to the statistics at the bottom of the main forum page, I am the only person out of 10,935 registered users with a birthday today.

Now, assuming that people have entered their actual birthday (and not 01/01/1970 or something) when registering, and assuming that our birthdays are evenly distributed throughout the year (ie the probability of any one person having a birthday today is 1/365), what are the odds of me being the only one to have a birthday today* out of almost 11,000 people ? I am also ignoring leap years.


It's making my head hurt trying to work it out.






* for the pedants... I mean celebrating the anniversary of my birth

[Kingstepper]

I imagine most people haven't entered their birthday - why would they?

Happy Birthday BTW!

[WORKSIMON]

Probably not worth worrying about

[amnesia]

I imagine most people haven't entered their birthday - why would they?

Happy Birthday BTW!

Well, let's assume that they have

(Thanks BTW)

[Dazzler]

Here's the birthday paradox to really cook your brain.

http://www.bbc.com/news/magazine-27835311
https://en.wikipedia.org/wiki/Birthday_problem

[Mr Curta]

In the region of 0.000000000000094. Probably.

[redmonaco]

Happy Birthday Amnesia!!!

[Bazzman]

Here's the birthday paradox to really cook your brain.

http://www.bbc.com/news/magazine-27835311
https://en.wikipedia.org/wiki/Birthday_problem

I just read this. My head really does hurt.

[jmarchitect]

Happy Birthday!

[catch21]

According to the statistics at the bottom of the main forum page, I am the only person out of 10,935 registered users with a birthday today.

Now, assuming that people have entered their actual birthday (and not 01/01/1970 or something) when registering, and assuming that our birthdays are evenly distributed throughout the year (ie the probability of any one person having a birthday today is 1/365), what are the odds of me being the only one to have a birthday today* out of almost 11,000 people ? I am also ignoring leap years....:

Pretty slim, Happy Birthday.

[Wolfie]

In the region of 0.000000000000094. Probably.

Does that make you feel special Amnesia???

Happy birthday

[amnesia]

Thanks for the birthday wishes chaps... I love you all.

I'm quite keen to understand the mathematics behind my probability question, though.

[MartynJC (UK)]

01/01/1970. Default birthday

[Mr Curta]

Thanks for the birthday wishes chaps... I love you all.

I'm quite keen to understand the mathematics behind my probability question, though.

(364/365)¹⁰⁹³⁴

[Possu]

(364/365)¹⁰⁹³⁴

Would this be the correct way to take leap years into account?

(364/365)^8200.5 x (365/366)^2733,5

Happy birthday amnesia!

[Deckard81]

I just read this. My head really does hurt.

So does mine...

Weird birthdays combo in my life:

My father and my father in law were born the same day, same year, roughly at the same time

At work (156 employees) 5 of us share the same birthday (all different years)

My wife and my best friend were born the same day (1 year apart)

My mum and my ex boss were born the same day (1 apart)

My guess is that it's human nature to focus on this coincidences and ignore everything else. But I was still really surprised about my dad and my father in law...

[vagabond]

Happy birthday Amnesia - I'd completely forgotten about it until you reminded me!

[soundood]

I share the same birthday including year of birth with Morten Harket,

[Mr Curta]

Would this be the correct way to take leap years into account?

(364/365)^8200.5 x (365/366)^2733,5

Leap years mean four days out of every 1461 that no other member can be born on.

(1457/1461)¹⁰⁹³⁴

[catch21]

Talking of strange coincidences, my mum and dad shared the same birthday, May the 5th.

Actually maybe not so much of a coincidence, that's why they went out together that first time...

[Velorum]

Happy birthday

I don't think that there is an even spread of births throughout the year - however, for you to be the only one of so many people seems rather odd

[PhilipK]

Leap years mean four days out of every 1461 that no other member can be born on.

(1457/1461)¹⁰⁹³⁴

I don't think that you have allowed for 2000 not having been a leap year (only years which are divisible by 4 but not by 400 are leap years).

[learningtofly]

I share my birthday with my brother, and my ex brother in law. That's pretty weird.

Oh, and many happy returns to the OP.

[Saint-Just]

I don't think that you have allowed for 2000 not having been a leap year (only years which are divisible by 4 but not by 400 are leap years).

I don't think we have many 17 year old around.

[VDG]

I'm surprised you've remembered it.

[submorstua]

Here's the birthday paradox to really cook your brain.

http://www.bbc.com/news/magazine-27835311
https://en.wikipedia.org/wiki/Birthday_problem

Ahhh I was going to bring up the birthday paradox. A very interesting phenomenon.

Happy belated birthday to the OP, too!

[submorstua]

Talking of strange coincidences, my mum and dad shared the same birthday, May the 5th.

Seems like a cool coincidence to me. My girlfriend and my mom share a birthday, which means I shouldn't ever forget (but if I did......).