Count the Observations

Count the total number of given data points, which gives $n = 7$.

$n = 7$

Arrange Data in Ascending Order

Sort the given numbers from smallest to largest: $11, 12, 14, 15, 17, 19, 21$.

$11, 12, 14, 15, 17, 19, 21$

Identify Median Position

Since $n$ is odd, use the formula to find the position of the median term.

$ext{\text{Position}} = \frac{7+1}{2} = 4^{\text{th}} \text{ term}$

Find the Median Value

Locate the 4th term in the sorted arrangement, which is $15$.

$M = 15$