Q.Find the mean deviation about the median for the data: $13, 17, 16, 14, 11, 13, 10, 9, 15$.

[!TLDR] Sort the data, find the median (middle value, $n=9$ odd), then average $|x_i-M|$. [!ANSWER] Median $=13$, Mean De …

Sorting the data $13,17,16,14,11,13,10,9,15$ in ascending order gives $9,10,11,13,13,14,15,16,17$. Since $n=9$ is odd, the median is the middle (5th) value: $M=13$. The absolute deviations from $M=13$, taken in this sorted order, are: $|9-13|=4$, $|10-13|=3$, $|11-13|=2$, $|13-13|=0$, $|13-13|=0$, $|14-13|=1$, $|15-13|=2$, $|16-13|=3$, $|17-13|=4$. Their sum is $4+ …

Arrange the data in ascending order, locate the median (the middle value for odd $n$, or the average of the two middle values for even $n$), …

The most common mistake is finding the median from the unsorted data (i.e. simply picking the middle-position value of the original list) instead of sorting first; …