The third quartile (rounded to the nearest tenth if needed) of the following data set is: 11, 20, 17, 8, 8, 9, 20, 13, 21.
8.5
8
20
14.1
To find the third quartile, we first need to find the median of the data set.
The data set in ascending order is: 8, 8, 9, 11, 13, 17, 20, 20, 21
There are 9 numbers in the data set, so the median is the middle number. In this case, the median is 13.
Now we need to find the median of the upper half of the data set, excluding the median itself.
The upper half of the data set is: 17, 20, 20, 21
There are 4 numbers in the upper half of the data set, so the third quartile is the median of the second half.
Median of the upper half = (17 + 20) / 2
= 37 / 2
= 18.5
So, the third quartile (Q3) of the data set is 18.5. (rounded to the nearest tenth)