Thread: it's that time again....How old are you and what do you do?
View Single Post
  #138  
Old 03-23-2007, 10:55 AM
Archive Archive is offline
Administrator
 
Join Date: Mar 2009
Posts: 58,359
Default it's that time again....How old are you and what do you do?
Posted By: Joe Tocco

The probability of any two people having the same birthday in a random sample is significantly greater than the probabliity of someone in that sample having your exact birthday. Assuming an equal distribution and ignoring leap years, the chance of someone having your birthday is 1/365. The chance of 1 or more people having your birthday out of a sample of 120 is 1-(364/365)^120, or about 28%. The formula for figuring if any two people have the same birthday is significantly more complicated, but comes out to about 99.99999998% for 120 people, or 62.7% for your example of 25 people in a elevator. Sorry for the derail, I'm a probability freak

Joe

Reply With Quote