Find the median of the data: 7, 15, 121, 50, 111, 81, 1, 17, 9, 15, 18

Given data: 7, 15, 121, 50, 111, 81, 1, 17, 9, 15, 18

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

1, 7, 9, 15, 15, 17, 18, 50, 81, 111, 121

Here, the number of observations is 11, which is odd.

Thus, median = 6th term

Median = 17.