Xi'an's Og

Consider a shell game with three shells and a ball with The Riddler constraint that the location of the shell with the ball is always exchanged with the location of an empty shell, randomly chosen. If one starts with the ball as rightmost, what is the distribution of the location of the ball after N steps?

Running an exploratory R code like

o=rep(0,3)
for(n in 1:1e6){
  b=c(0,0,1)
  for(t in 1:N){
    i=sample((1:3)[!b],1);b=0*b;b[i]=1}
  o=o+b}

shows that the difference in probability is between the rightmost position and both others, starting at zero, and evolving as p⁺=(1-p⁻)/2, with the successive values 0,1/2,1/4,3/8,5/15,11/32,… Very quickly converging to 1/3.

This entry was posted on August 10, 2022 at 12:22 am and is filed under Books, Kids, pictures, R, Statistics with tags Australia, combinatorics, Gold Coast, R, riddle, shell game, The Riddler, thimblerig. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.