<Dl> <Dd> Q 1 = (σ z 1) + X (\ displaystyle Q_ (1) = (\ sigma \, z_ (1)) + X) </Dd> </Dl> <Dd> Q 1 = (σ z 1) + X (\ displaystyle Q_ (1) = (\ sigma \, z_ (1)) + X) </Dd> <P> and the third quartile </P> <Dl> <Dd> Q 3 = (σ z 3) + X (\ displaystyle Q_ (3) = (\ sigma \, z_ (3)) + X) </Dd> </Dl>

The difference of the range and the interquartile range of the data set represented by the box plot