Arrange in Ascending Order

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

$11, 12, 15, 19, 21$

Count Observations

The total number of observations is $N = 5$, which is an odd number.

$N = 5$

Find Median Position

For an odd number of terms, apply the formula for the median position: $\frac{N + 1}{2}$.

$\text{Position} = \frac{5 + 1}{2} = 3^{\text{rd}} \text{ term}$

Extract the Median

The value of the $3^{\text{rd}}$ term in the sorted list is $15$.

$\text{Median} = 15$