Percentiles of a Distribution

The p-th percentile of a distribution marks the point such that p% of the values are below it.

Example:

Let’s say $n_p$ is $7.9$. The value corresponds to about 0.3. Thus, the shaded area is 0.3 of the entire distribution. Thus, $n_p$ is in the 30th percentile (Percentiles of a Distribution) of the distribution.