This applet simulates Galton's Board, in which balls are dropped through
a triangular array of nails. This device is also called a **quincunx**
. Every time a ball hits a nail it has a probability of **50 percent to
fall to the left** of the nail and a probability of **50 percent to
fall to the right **of the nail.

The piles of balls which accumulate in the slots beneath the triangle will resemble a binomial distribution. To reach the bin at the far left the ball must fall to the left every time it hits a nail.

Because Galton's board consists of a series of experiments the piles
in the slots are the sum of 10 random variables. Therefore, this simulation
provides also an __illustration of the central-limit theorem__
, which states that the distribution of the sum of *n* random variables
approaches the normal distribution when *n* is large. When we add
more rows of nails to the board the approximation would be better.