Find out range and semi inter-quartile range (Q) from the following items .
9, 15 , 12 , 21 , 8 , 17 , 20

Explanation

Range = highest value - lower value
= 21 - 8 = 13
`Q = (Q_(3) - Q_(1))/(2)`
`Q_(1) = 9 , Q_(3) = 20`
`Q = (20-9)/(2) = (11)/(2) = 5.5`.