The simulation above represents 20 marbles dropped 5 at a time onto a board with pegs, a Galton board. You are attempting to find the postion at which the balls are released but you can only measure the average distance of the balls after they have made it though the pegs. Each time the marble hits a peg it has an equal chance of bouncing to the left or to the right. At any time you can measure the mean, i.e. average, value of the position of the marbles that have made it through the pegs. The simulation will stop after all 20 marbles have landed but you may repeat the experiment as many times as you wish.
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Galton board used with permission of the author, David Krider.