Quartile

One of the four divisions of observations which have been grouped into four equal-sized sets based on their Rank. The quartile including the top Ranked members is called the first quartile and denoted $Q_1$. The other quartiles are similarly denoted $Q_2$, $Q_3$, and $Q_4$. For $N$ data points with $N$ of the form $4n+5$ (for $n=0$, 1, ...), the Hinges are identical to the first and third quartiles.

See also Hinge, Interquartile Range, Quartile Deviation, Quartile Variation Coefficient