Brownian Motion - Normal Increments

From this 2000 point graph of Brownian motion
on the left is the graph of the increments Y(t + 10) - Y(t). We say this is an increment with delay = 10. Compare this with the right graph, the increments Y(t + 50) - Y(t), plotted to the same scale.
To compare the distributions of these increments, divide the range of the increments into 100 bins and plot the histograms of the number of increments in each bin.
On the left is the histogram of the delay = 10 increments, right is the histogram of the delay = 50 increments.
Both are approximately normal.
The second is wider than the first, in fact, its standard deviation is about 2.25 times that of the first.
Note 2.25 is close to √5.

Return to Mathematical Properties of Brownian Motion.