Archive for birthday cake
Charlie, the next generation [cover]
Posted in Books, Kids, pictures with tags 7 janvier 2015, anniversary, birthday cake, Charlie Hebdo, cover, France, freedom of religion or belief, freedom of speech, fundamentalism, high school, Je suis Charlie, religions, terrorism on January 7, 2025 by xi'anbirthday paradox, one by one
Posted in Books, Kids, pictures, Statistics with tags birthday cake, birthday problem, codegolf, FiveThirtyEight, R, The Riddler on November 1, 2022 by xi'an
An easy riddle, riding the birthday paradox. Namely how many people on average have to sequentially enter a room for a double birthday to occur?
The answer is straightforward,
as only the last person in can share a birthday with those already in. This sum equals 24.62. Since the “magic number” is 23, this may sound wrong but the median attached to the above distribution is truly 23. My R code is
q=rep(1,a<-366)/365 for(n in 3:a)q[n]=q[n-1]*(1+1/(n-2)-(n-1)/365) sum(q[-1]*(2:a))

