Quartile deviation
It represents the difference between third quartile and first quartile.
Q.D. = Q3 –Q1 / 2
Coefficient of Quartile deviation;-
= Q3 –Q1/ Q3+ Q1
Q3 = 3N/4
Q3= L + 3N/4 – c.f.
______________ * H
F
Q1 = N/4
Q1= L + N/4 – c.f.
______________ * H
F
L = Least value
C.F. = cumulative frequency
F = Frequency
H = class interval
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