Definition:Quartile/First

Definition
Let $D$ be a finite collection of data regarding some quantitative variable.

The first quartile of $D$ is defined as the median of the data values in $D$ below and not including the second quartile $Q_2$.

It is commonly denoted $Q_1$.

Also known as

 * The first quartile is often referred to as the lower quartile.

Also see

 * Definition:Interquartile Range
 * Definition:Second Quartile
 * Definition:Third Quartile