Statistics
Percentile rank with the sample convention
Divides by one less than the group size, treating the group as a sample. For 12th out of 250 this gives 238 / 249 = 0.9558232931726908.
The Formula
PR = count below / (n - 1)
Divides by one less than the group size, treating the group as a sample. For 12th out of 250 this gives 238 / 249 = 0.9558232931726908.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| PR | Percentile rank as a proportion | dimensionless | 0.9558232931726908 for the worked case; multiply by 100 for the percentage form. |
| count below | Number of values strictly below the value of interest | count | 238 when the value ranks 12th out of 250. |
| n | Size of the group | count | 250 in the worked case, so the denominator is 249. |
What Each Symbol Means
PRdimensionless
Percentile rank as a proportion
0.9558232931726908 for the worked case; multiply by 100 for the percentage form.
count belowcount
Number of values strictly below the value of interest
238 when the value ranks 12th out of 250.
ncount
Size of the group
250 in the worked case, so the denominator is 249.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate a percentile rank page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate A Percentile Rank, filed under Education. Every number the guide produces comes from substituting into this one line.