Arranging the given observations in ascending order, we have 7, 9, 11, 12, 15, 18, 20, 23.
Here n = 8 (n is even)
`therefore` first quartile, `" "Q_(1) = ((n)/(4))"th"" ""item" = ((8)/(4))"th item"`.
`" ""second observation of the data, i.e., 9"`.
`" "therefore Q_(1) = 9`.
