Question

Find out the quartile deviation for the given individual observations: 10,20,30,40,50, 60,70

Answer 1

For the given data, N = 7

$Q_1=\text{Size of}\left(\frac{N+1}{4}\right)th\text{item}=\text{Size of}\left(\frac{7+1}{4}\right)th\text{item= Size of 2nd item = 20}\therefore Q_1=20\text{and}{Q}_3=\text{Size of}\frac{3(N+1)}{4}th\text{item}=\text{Size of}\frac{3(7+1)}{4}th\text{item = Size of 6th item = 60}\therefore Q_3=60\text{Now,}QD=\frac{Q_3-Q_1}{2}=\frac{60-20}{2}=\frac{40}{2}=20$