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

• Results about quartiles can be found here.

Sources

• 1989: Ephraim J. Borowski and Jonathan M. Borwein: Dictionary of Mathematics ... (previous) ... (next): quartile
• 2011: Charles Henry Brase and Corrinne Pellillo Brase: Understandable Statistics (10th ed.): $\S 3.3$