What is the median of the following data set?
4, 4, 4, 5, 7, 8, 10, 14, 18, 20, 26, 30
4
9
17
30
34
9 : median = (12 + 1) / 2 = 6.5 th observation ; then average of 6th and 7th observations : (8 + 10) / 2 = 9
