Answer:
17.5
Explanation:
The median is the value that separates the higher half from the bottom half of the data sample (middle value).
We have
15, 8, 19, 21, 18, 17
Write from the smallest to the largest number
8, 15, 17, 18, 19, 21
We have an even number of numbers. Therefore we calculate the arithmetic mean of the two middle numbers:
8, 15, 17, 18, 19, 21
(17 + 18) : 2 = 35 : 2 = 17.5