The Percentile function computes the specified percentile of the specified random variable or data set.

The first parameter can be a data set (e.g., a Vector), a Matrix data set, a distribution (see Statistics[Distribution]), a random variable, or an algebraic expression involving random variables (see Statistics[RandomVariable]).

The second parameter p is the percentile.

For a description of the available options, see the Statistics[Quantile] help page. Calling Percentile with percentile $p$ is equivalent to calling Quantile with probability $0.01p$.

with(Statistics):

Percentile(Weibull(a, b), 30);

$a{\ln \left(\frac{10}{7}\right)}^{\frac{1}{b}}$

Percentile(Weibull(3, 5), 30);

$3{\ln \left(\frac{10}{7}\right)}^{\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$5$}\right.}$

Percentile(Weibull(3, 5), 30, numeric);

$2.44104494075064$

StandardError[10^5](Percentile, Weibull(3, 5), 30);

$\frac{6\sqrt{\frac{21}{10000000}}}{7{\ln \left(\frac{10}{7}\right)}^{\raisebox{1ex}{$4$}\!\left/ \!\raisebox{-1ex}{$5$}\right.}}$

StandardError[10^5](Percentile, Weibull(3, 5), 30, numeric);

$0.00283364066608145$

A := Sample(Weibull(3, 5), 10^5):

Percentile(A, 30);

$2.44048423337317$

StandardError[10^5](Percentile, A, 30);

$0.00259397498616096428$

M := Matrix([[3,1130,114694],[4,1527,127368],[3,907,88464],[2,878,96484],[4,995,128007]]);

$M≔\left[\begin{array}{ccc}3& 1130& 114694\\ 4& 1527& 127368\\ 3& 907& 88464\\ 2& 878& 96484\\ 4& 995& 128007\end{array}\right]$

Percentile(M, 29);

$\left[\begin{array}{ccc}2.88000000000000& 903.520000000000& 95521.6000000000\end{array}\right]$

Stuart, Alan, and Ord, Keith. Kendall's Advanced Theory of Statistics. 6th ed. London: Edward Arnold, 1998. Vol. 1: Distribution Theory.

The A parameter was updated in Maple 16.