This is an example of a random variable and is approximated by the probability distribution called normal or Gaussian distribution. PLINCO! The ball can land in randomly in any of 10 catches. So all things being equal there is a 10% chance that the ball will land in any of the catches. BUT start closing off some of the catches and everything changes. 10 catches open out of 10 = each catch has 10% chance of winning 9 catches open out of 10 = each catch has 11.1% chance of winning 8 catches open out of 10 = each catch has 12.5% chance of winning 7 catches open out of 10 = each catch has 14.3% chance of winning 6 catches open out of 10 = each catch has 16.6% chance of winning 5 catches open out of 10 = each catch has 20% chance of winning 4 catches open out of 10 = each catch has 25% chance of winning 3 catches open out of 10 = each catch has 33.3% chance of winning 2 catches open out of 10 = each catch has 50% chance of winning 1 catch open out of 10 = catch has 100% chance of winning