mjs82 wrote:
It's all to do with probabilities. At first glance the odds would appear to be as some have suggest, 1 in 365.25. But, this does not take into account the principal of stacked arrays:
For a 23 group sample:
(1) Probability of at least one coincident birthday
This is 1 - Pr(no coincident birthday), where the lack of a coincident birthday leads to an occupancy diagram of
[1,..,1] [0,...,0]
(23) (342)
U is then 365!/(23!342!), while B is 23!/(1!)23 (0!)342 = 23! and thus Pr(no coincident birthday) = 365-23 x 365!/342! = 0.493, so that Pr(>1 coincident birthday) = 0.507, from which the original Birthday Paradox follows.
Sorry for my late reply, I only just stumbled over this thread again for the first time in weeks.
I'll trust you that that makes sense. It looks scientific-y, so you are either a genius at math or a genius at beloney-ing.
when the need arises, i can do one or the other. on special occassions, even both. as my mother dearest always said, life is like an internet aspeger's forum. you never know who you're gunna get.