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Birthday

PostPosted: 01 Jan 2016, 18:20
by Andyp
With only 296 members it is amazing how many of them share the same birthday ;)

Re: Birthday

PostPosted: 01 Jan 2016, 19:56
by Doug
Andyp wrote:With only 296 members it is amazing how many of them share the same birthday ;)


& 8 of them born in the same year :!: & congratulations to the 111year old :eusa-liar:

Re: Birthday

PostPosted: 01 Jan 2016, 20:59
by Pinch
I used to study astrology and the Tarot - many moons ago when I was going through my hippy spiritual Goth years! :shock:

Andy, which zodiac star sign is the most popular amongst the members?

Re: Birthday

PostPosted: 01 Jan 2016, 22:25
by chataigner
Late september - early october perhaps ?

Re: Birthday

PostPosted: 02 Jan 2016, 00:53
by RogerS
Pinch wrote:....
Andy, which zodiac star sign is the most popular amongst the members?


Torus :D

Re: Birthday

PostPosted: 02 Jan 2016, 12:43
by Phil
RogerS wrote:
Pinch wrote:....
Andy, which zodiac star sign is the most popular amongst the members?


Torus :D


Which "Torus" would that be?

Must be the one without the couilles? :lol:

Cheers
Phil

Re: Birthday

PostPosted: 02 Jan 2016, 13:36
by Andyp
Pinch wrote:I used to study astrology and the Tarot - many moons ago when I was going through my hippy spiritual Goth years! :shock:

Andy, which zodiac star sign is the most popular amongst the members?


Sorry Paul, that would take me too long to work out. There are plenty of hairies around here though :D And probably one or two saggy teary * too :D

Re: Birthday

PostPosted: 09 Jan 2016, 21:32
by Gill
You only need 23 people on a forum for it to be probable that two of them will share the same birthday.

Re: Birthday

PostPosted: 10 Jan 2016, 11:05
by Andyp
I've read and tried to understand that fact Gill. It appears that with a group of 23 there is a 50% change of two people having the same birthday. No matter how hard I try or how many times I have read the explanation I can still not get my head around that. But then ignorance is bliss :D

Re: Birthday

PostPosted: 10 Jan 2016, 13:43
by Phil
Gill wrote:You only need 23 people on a forum for it to be probable that two of them will share the same birthday.



I have also tried to get my mind around this one.

On average there are 30.4375 days per month and 12 months of the year.

Is it not the 30.4375 to a factor of 12?

Cheers
Phil
One who has imbibed a certain amount of alcoholic substance with Sunday lunch ...................

Re: Birthday

PostPosted: 10 Jan 2016, 14:52
by chataigner
The way I see it, if "x" has a given birthday, then there is a 1 in 365 chance that "y" will have the same. Is it not then 2 in 365 or 1 in 182.5 for a 50% chance of having the same ? Or is that too simple ?

Re: Birthday

PostPosted: 10 Jan 2016, 15:03
by chataigner
chataigner wrote:The way I see it, if "x" has a given birthday, then there is a 1 in 365 chance that "y" will have the same. Is it not then 2 in 365 or 1 in 182.5 for a 50% chance of having the same ? Or is that too simple ?


I've just read the explanation, clearly it is too simple ! 1 in 365 (ish) is of course correct for 100% probability of two people having the same birthday, but a 50% probability does not equate to half a 100% probability.

Re: Birthday

PostPosted: 10 Jan 2016, 15:20
by chataigner
It's taken a few minutes, but I think I've understood it and can express it in words. You start by comparing two people - so far easy, when you add a third, you are not comparing the third only with the first, but also with the second. When you add a fourth, he is compared with each of the 3 others and so on.

Am I getting warm ?

Re: Birthday

PostPosted: 10 Jan 2016, 16:26
by Pinch
My head hurts :eusa-think:

Re: Birthday

PostPosted: 10 Jan 2016, 17:35
by Andyp
There are a number of explations available, here is one of them

http://betterexplained.com/articles/und ... y-paradox/

I still dont get though :oops:

Re: Birthday

PostPosted: 11 Jan 2016, 06:43
by Phil
Andyp wrote:There are a number of explations available, here is one of them

http://betterexplained.com/articles/und ... y-paradox/

I still dont get though :oops:



Thank you for that link - it is definitely far too early in the morning to try and understand.

Cheers
Phil (confused) :?

Re: Birthday

PostPosted: 11 Jan 2016, 09:15
by StevieB
You are perhaps thinking the question is: of the other 22 people in the room, what is the chance one of them will share MY birthday. The actual question is what is the chance that ANY two people will share the same birthday. Because you are taking all pair-wise comparisons, you are actually comparing 253 possibilities.

Although you can use simple probability to calculate this, the data is also slightly skewed by not every day having an equal chance of people being born on it - think of the boom in babies in September for example (Christmas is 9 months before) or the smaller boom in April/May (if it was a hot summer the year before).

Statistics can be wonderful and bloody useless at the same time. Did you know the mean number of legs a human has is less than 2? This is because some people have one leg or no legs, but nobody has 3 legs!

Steve