Find the median of the data:   12, 12, 31, 35, 66, 9, 53, 64,2, 11

21.5

Given data: 12, 12, 31, 35, 66, 9, 53, 64, 2, 11

Now, arrange the data in ascending order, we get:

2, 9, 11, 12, 12, 31, 35, 53, 64, 66

Here, the number of observations is 10, which is even

Thus, median = \(\frac{ 5th + 6th }{2}\)

Median = \(\frac{ 12 + 31 }{2}\)

Median = 21.5.