How many people have to be in a class so that there is a 50% chance that at least 2 people have the same birthday?
is this a riddle?
it's a riddle.. satellite is stuck in the middle.. o_O
xD
haha @saifoo.khan
more of a conundrum :) a coworker is taking an online stats course and asked me this question there is no "correct" answer that i know of, but is meant to exhibit intuition versus reality i think
i will be quiet because i know the answer will post a problem from dylan that took much of the morning
Reality is a bit painful, I do say.
oh so it is an honest question, not a riddle answer is 23
well i know if there are 366 people then 100% 2 people share same birthday :)
its easy
23 could be plausible, any logic to back it hto?
lgba, lol; yes 266 to be 100%
366 that is
Logic is overrated.
but the "at least part" hmmm
correct @amistre64
then maybe 183 people then 50% chance? hehe
I got this! \[\huge1-e^{-x^2(730.5)}\]
it is a calculation, for which you definitely need a calculator
Yay for paying attention in class :D
id say intuitively, you need at least 2 people :)
FYI: 365.25 days in a year
but isnt that 1/365 x 1/365 chance? :O
thats what i thought too
Leap year yo :-P
pass to the compliment, i.e. consider the probability that no two people have the same birthday am using 365 with no stupid leap year to make calculation easier
ah yes, the compliment
Aww nobody wants to dispute my expression eh? :-P
its a cute expression lol
if there are say \(n\) people then the probability no two people have the same birthday is \[\frac{365\times 364\times 363\times ...\times (365-n+1)}{365^n}\]
@amistre64, I've never understood this. Why is your picture an integral?
(I should also be asking why @satellite73 is using a bike.)
its not, thats my profile angle ;)
now it is a matter of computing for various choices of \(n\) and recalling that this is the compliment.
having a + sign just seemed to remedial
42.
this is the bike that i took from amistre because he did not let me ride the bike they gave him for this 1000 medal (back in the day)
You two have such a good relationship. I am jealous.
it tooks years of mistrust and antagonism to build this relationship as strong as it is lol
he is the older brother i never had
o_o
Loki and Thor :D
cain and able is what i had pictured, but pagan dieties work too :)
@agentx5 is that for real?
Medalling @amistre64 for his contribution to @satellite73's brotherly needs.
Is what for real? The expression I wrote?
i was thinking more of abbot and costello http://www.youtube.com/watch?v=KVn0aksCzNE&feature=related
Every time I hear "for real" on this site, I immediately think of \(\mathbb{R}\)...
If you make it into a standard y=f(x) function I believe it gives you the answer for any input, provided you use a ceiling or floor function to make it into whole #'s :-)
yeah the integral so probability you get no two birthdays the same with \(x\) people is \(e^{-750x^2}\)?
poisson?
no that can't be it
Of course somebody has already done this and uploaded it :-D I was trying to give you all a graph in Wolf but it wasn't understanding what I was asking it to do I guess, kept graphing the wrong thing
Hehe, now this is more interesting: http://en.wikipedia.org/wiki/Birthday_attack
23 according to wikipedia
I knew that it was a surprisingly few, but didn't realize it could be that small of a number.
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