PPT Slide
2. Ranking the deviations
If we have a set of n d(observed) values, and we sort them into ascending order, they will range from about -4 to +4, and cluster around 0.0. Their frequency should follow a normal distribution. If we number the sorted values from i = 1 to n, the rank order fraction
r is the fractional distance from the central value around d = 0.0