The range is the difference between the largest and smallest values in the data set.

The lower quartile (\(Q_1\)) is the value which lies a quarter of the way in when values are arranged in ascending order in a data set.

It is the value equal to \(\dfrac{n+1}{4}\).

The upper quartile (\(Q_3\)) is the value which lies three quarters of the way in when values are arranged in ascending order in a data set.

It is the value equal to \(\dfrac{3(n+1)}{4}\).

The inter-quartile range (\(IQR\)) is equal to the difference between the upper and lower quartiles.