Elementary Statistics (1+1)

7.1.4 Quartile Deviation

Quartile deviation or semi-interquartile range Q is given by

Q = ½ (Q₃-Q₁)

where Q₁ and Q₃ are the first and third quartiles of distribution respectively.

Quartile deviation is definitely a better measure than the range as it makes use of 50% of the data. But since it ignores the other 50% of the data, it cannot be regarded as a reliable measure.