The Rank Ordered Centroid equation computes some number, n, which is a value that estimates the distance between adjacent ranks on a normalized scale e.g. running from 0 to 1. Moreover, this is used in modeling human decision logic.
This equation is often used to generate a modeled relative ranking between a set of criteria. It is used when there is no data, time, or resources to do an exhaustive comparison of the criteria. This method has been found to generate a distribution of criteria weightings that is statistically comparable to that generated by teams or panels of subject matter experts performing various algorithmic approaches to defining relative weights.
To use the equation you simply order the criteria from 1 through n with no regard for how much each criteria might differ in weight pairwise from any other criteria. If you have seven criteria for example you just have to order them 1 through 7 in order of highest criteria importance.
Then you generate the Rank Order Centroid sequence of weights for the input number 7. The resulting sequence of weights are then assigned to the ordered criteria.