Merits and Demerits of Quartile Deviation

Merits:

• It is rigidly defined.
• It is superior to range in as much as its calculation is based on middle 50% of the items of a series.
• It is easy to calculate, and especially in case of an open end series, no 50% of the items of a series.
• It is not very much affected by the extreme values of  a series.
• In a moderately symmetric series, it helps in the computation of the lower quartile, upper quartile, standard deviation, and mean deviation in the direct manner by the models as follows:

Q₁ = M – QD

Q₃ = M + QD

S.D., or  =3/2 QD        and MD or = 6/5 QD.

• It can be determined, even if, the first 25% and the last 25% of the items are replaced or deleted.

Demerits

• It is not based on all the observations of a series.
• It is not capable of further algebraic treatment.
• It is affected by fluctuations in sampling.
• It is not understood by a common man.
• It does not exhibit any scatter around an average for which is remarked as a measure of partition rather than a measure of dispersion.
• It takes more time to calculate as its calculation involves finding out of the values of the lower quartile, and upper quartile.