Explanation : First we need to sort the data in ascending order: -21, -12, 3, 6, 8, 10,
11, 12, 15, 32. The third quintile corresponds to the 60th percentile. The
location of the 60th percentile is given by: L60 = (10 + 1)60/100 = 6.6.
The value is estimated using linear interpolation: P60 = 10 + 0.6(11– 10)
= 10.6.