The x-axis shows the number of 6's I got out of 100 throws. The y-axis shows how many times I got that number. This is no accident. This is a deep result which lets us analyze the error in our estimate of the true probability. It is roughly given by the spread of the normal distribution about its average value.
Exercise Look up the formula for a normal distribution.
See if you can estimate the average and the standard deviation by comparing the formula to the graph above. You may want to plot them on the same graph and adjust the strength, mean, and standard deviation of the normal distribution so that it looks like the data. Now you know how random numbers are calculated on a computer and a little about how to analyse the results of statistical experiments. Let's move on to computing something. This example involves calculating the area of a circle.