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“Put the two together to find the odds of NOT finding at least two kids with the same birthday in a group of 30 kids:
There’s about a 30% chance that you will NOT find at least two kids who share the same birthday in a group of 30. Therefore the opposite situation, that you WILL find at least two kids with the same birthday in a group of 30, is a whopping 70% (1 – .3 = .7). In fact, we find that in a group of 23 kids, your odds are better than 50% to find at least two people with the same birthday.”
From a mathematics web site^^^^^^^^^^^^^^^
lech,
you are correct,
it is much higher.
I didn’t take into account that “variable change”,
in this case
as you proceed down the line of people,
as you find a person that does not share the same
birthday, the chances of the next one NOT having the same birthday actually decrease.
like snappy said, now I’m getting a headache!
I once made the mistake of asking my brother the mathematician about the Monty Hall problem.
He said there was some debate among mathematicians whether that answer was correct. Then he went on for an hour about it and I didn’t understand a word he said.
He also sends me his papers. I can read the acknowledgment section.
I think there’s a lot of Cataphilia already on the OT
Resorting to the Internets:
http://en.wikipedia.org/wiki/Birthday_problem
legion – probability of same birthday with 30 people is much higher than 1 in 12
::brain going all fuzzy and stoopid from math. grabbing beer from fridge.::
etson,
I recall what you were talking about:
variable change.
If you have three curtains with a prize behind one.
You choose curtain number one.
The host tells you that if you choose one of the other two curtains you could win double.
Discard the first and go for the 2 or 3rd because now that the host has introduced the variable change condition into the equation you have reduced the chances of winning to 1 in 2 from 1 in 3.
The choice becomes keep 1 and remain at your chances of 1 in three
or change
and pick one of the others since the chance of winning is now winning on the change itself.
Note:
I shared the same math class with the Westinghouse winner for my graduating year at Brooklyn Tech. He developed his own math theorem.
No joke,
It was survival of the fittest in that class.
alright,
you all are forcing me into math nerd mode,
so here goes.
person one birthday is a given date, say 1/1
person two’s chance of having the same month is
1/12
person two’s chance of having the same day in that month is
1/30
1/12 X 1/30 = 1/360
BUT here’s the kicker, there are 30 people in the room
so that changes the mathematics completely
1/360 X 30/1= 1 in 12
So there. ;o)