distribution respectively and Q – Q is called as inter quartile range. (i) Relative measures for QD Quartile deviation is an absolute measure of dispersion. The relative measure corresponding to this measure, called the coefficient of quartile deviation is calculated as follows: Coefficient of QD = Q Q Q Q – Coefficient of quartile deviation can be used to compare the degree of variation in different distributions. (ii) Computation of Quartile Deviation The process of computing quartile deviation is very simple since we just have to compute the values of the upper and lower quartiles that is Q and Q respectively.
Example . Calculate the value of quartile deviation and its coefficient from the following data Roll No. Marks Marks are arranged in ascending order n = number of observations = Q = Size of th b ] g l value = Size of th l value = Size of nd value = Hence Q = Q = Size of th b ] g l value = Size of th l value = Size of th value = Hence Q = - - QD = ( Q – Q )= = . Coefficient of QD = Q Q Q Q = .
Hence coefficient of QD = . Example . Compute coefficient of quartile deviation from the following data Marks No. of Students Marks Frequency Cumulative Frequency cf N