\begin{definition}[Definition:Median (Statistics)]
Let $S$ be a set of quantitative data.
Let $S$ be arranged in order of size.
The '''median''' is the element of $S$ that is in the '''middle''' of that ordered set.
Suppose there are an odd number of element of $S$ such that $S$ has cardinality $2 n - 1$.
The '''median''' of $S$ in that case is the $n$th element of $S$.
Suppose there are an even number of element of $S$ such that $S$ has cardinality $2 n$.
Then the '''middle''' of $S$ is not well-defined, and so the '''median''' of $S$ in that case is the arithmetic mean of the $n$th and $n + 1$th elements of $S$.
\end{definition}