Answer:
Median: 17
Mean: 16
Explanation:
Median is the "middle number" or the average of the 2 middle numbers if the set has an even number of entries
(11+23)/2=34/2=17 which is the median
The mean is all the entries added up divided by the number of entries
(5+23+11+15)/2=64/4=16 which is the mean