In the data set below, what is the interquartile range?

1 1 1 2 3 3 3 5 8

The interquartile range is the difference between the third quartile (Q3) and the first quartile (Q1).

Q1 = 1
Q3 = 3

Interquartile Range = Q3 - Q1
Interquartile Range = 3 - 1
Interquartile Range = 2

Therefore, the interquartile range of the data set is 2.