Answer :
The median of a data set is the number in the middle of a list when the data set is ordered from smallest to largest.
To find the median, list the numbers from least to greatest value:
[tex]8,9,9,10,10,11,12,12,12,12,14,15,15,17,18[/tex]The list has 15 elements, then, the element in the middle of the list is the number:
[tex]\frac{15-1}{2}=\frac{14}{2}=7\text{ th}[/tex]The 7th element of the list is 12.
Therefore, the median of the data set is 12.