The numbers are: 3, 10, 6, 11, 14, 17, 9, 8, 12.
The mean of the numbers is:
\[
\text{Mean} = \frac{3 + 10 + 6 + 11 + 14 + 17 + 9 + 8 + 12}{9} = \frac{90}{9} = 10
\]
Now, calculate the absolute deviations from the mean:
\[
|3 - 10| = 7, \quad |10 - 10| = 0, \quad |6 - 10| = 4, \quad |11 - 10| = 1, \quad |14 - 10| = 4
\]
\[
|17 - 10| = 7, \quad |9 - 10| = 1, \quad |8 - 10| = 2, \quad |12 - 10| = 2
\]
The sum of the absolute deviations is:
\[
7 + 0 + 4 + 1 + 4 + 7 + 1 + 2 + 2 = 28
\]
The mean deviation is:
\[
\frac{28}{9} \approx 3.1
\]