Arrange Data in Order

Sort the given data set in ascending order: $12, 21, 23, 34, 45, 56, 67, 89, 90$.

$12, 21, 23, 34, 45, 56, 67, 89, 90$

Count Observations

Determine the total number of observations, which is $N = 9$ (an odd number).

$N = 9$

Find Median Position

Apply the median position formula for odd $N$: $\frac{N + 1}{2} = \frac{9 + 1}{2} = 5$.

$\text{Position} = \frac{9 + 1}{2} = 5$

Determine Median Value

Identify the 5th term in the sorted sequence, which is $45$.

$\text{Median} = 45$