Percentile Ranking is a standardized ranking. The first (best) observation is ranked observation with largest numerical value is ranked one; the worst one with smallest numerical value is ranked 100. The rest of the observations are placed an equal distance from each other.
(Remember the case of standard deviation, the best fund is not ranked #1)
Sort values according to selection: ascending or descending
Count the total number of distinct observations (n)
Calculate Percentile Ranks for each value from top to bottom,
FLOOR[] = function that rounds down to the nearest integer
i = ith value
Calculation of the Breakpoints of X-tiles (for deciles, quintiles and quartiles)
Given an array of values, 
, do the following to find the breakpoints of X-tiles.
1. Sort all the values from the smallest to the largest, resulting in 
.
2. Calculate the quantile of the values by
3. Calculate the (qth) breakpoints by
If 
(minimum), then, let
.
Otherwise, if 
(maximum), then, let
.
Otherwise, if 
(median), then, let
.
Otherwise, if 
such that 
, then, let
.
Otherwise, find an 
such that 
, and 
, then, let
, and 