Posted by JohnX2 on March 22, 2002, at 0:57:18
In reply to Re: 70% - Bingo! But how??, posted by Cass on March 21, 2002, at 21:40:51
> Was that a math problem, or was there a trick to it? How do you calculate it?
Some teacher quoted this to me.
I was a bit dubious.I wrote a small "C" computer program that does a brute force random simulation of the problem at hand. Basically pick a random number 1-365 and assign it to 30 variables (i.e. people). Do some cross-checking for matches. Do this a zillion times and collect the hit rate. My simulation settles at around 70.6%. I think there may be some skew from a crummy random number generator.
I also tried to figure out the formal math proof (a bit more tricky since I haven't done stats in a while). The trick is to figure out the odds of no one having the same birthday and then just subtract this answer from 100%. This gives the same answer and is much easier. My best formal proof that I came up with in the past hour gave an answer of 72%. (Although I still feel it requires more introspection, I was hoping it would correlate better with my computer run).
Sorry for the boring programming/math. I get bored. Seems I have been away from my job for too long (engineering). May be time to return to work.
Regards,
John
poster:JohnX2
thread:20576
URL: http://www.dr-bob.org/babble/social/20020320/msgs/20616.html