Quartile Deviation (Q.D) - meaning, merits and Demerits

Quartile Deviation (Q.D) - Meaning, Merits and Demerits

Quartile Deviation: The QD is half of the difference between the upper and lower quartiles. Symbolically, 

                        QD= ½ (Q3- Q1)

       

Quartile Deviation is an absolute measure of dispersion. The relative measure corresponding to QD, called the coefficient of QD, is obtained by applying the following formula:

Coefficient of Range= (Q3 - Q1) / (Q3 Q1)

Coefficient of QD can be used to compare the degree of variation in different distributions.

Merits of Quartile Deviation:

1. It is based on 50% of the observations.

2.  It is not affected by the presence of extreme values.

3. In case of open-end distribution, it can be computed.

Demerits of Quartile Deviation:

1. It is not based on each and every item of the distribution.

2. It is not capable of further algebraic treatments.

3. The value of Range is affected more by sampling fluctuations