Editing Percentile (section)

==={{anchor|Weighted percentile}}The weighted percentile method===
{{see also|Weighted median}}
In addition to the percentile function, there is also a ''weighted percentile'', where the percentage in the total weight is counted instead of the total number. There is no standard function for a weighted percentile. One method extends the above approach in a natural way.

Suppose we have positive weights <math>w_1, w_2, w_3, \dots, w_N</math> associated, respectively, with our ''N'' sorted sample values.  Let
: <math>S_N = \sum_{k=1}^N w_k,</math>
the sum of the weights.  Then the formulas above are generalized by taking
: <math>p_n = \frac{1}{S_N}\left(S_n - \frac{w_n}{2}\right)</math> when <math>C=1/2</math>,
or
: <math>p_n = \frac{S_n - Cw_n}{S_N +(1-2C)w_n}</math> for general <math>C</math>,
and
: <math>v = v_k + \frac{P - p_k}{p_{k + 1} - p_k}(v_{k + 1} - v_k).</math>

The 50% weighted percentile is known as the [[weighted median]].