Sort the Data

Arrange the given 10 observations in ascending order: 9, 12, 12, 21, 25, 31, 34, 45, 56, 99.

$9, 12, 12, 21, 25, 31, 34, 45, 56, 99$

Identify Position

Since the number of observations $n = 10$ (which is even), the median is the average of the $5^{th}$ and $6^{th}$ observations.

$n = 10$

Calculate Median

The $5^{th}$ term is $25$ and the $6^{th}$ term is $31$. Calculating the average: $\text{Median} = (25 + 31) / 2$.

$\text{Median} = \frac{25 + 31}{2} = \frac{56}{2} = 28$