Find semi-inter quartile range of the following data :

Explanation

Here , N = 60
`therefore Q_(1) = ((N)/(4))` th item = `((60)/(4))` th item = 15th item
`therefore Q_(1) = 6` (as the 15 th item lies 21 in the cumulative frequency )
`Q_(3) = 3((N)/(4))` th item = 45 th item
`therefore Q_(3) = 9 ` (as 45 th item lies 48 in the cumulative frequency)
Semi -inter quartile range (QD) = ` (Q_(3) - Q_(1))/(2) = (9 - 6)/(2) = 1.5`.