Final answer:
The interquartile range is the difference between the third quartile and the first quartile. For this data set, the interquartile range is 7.
Step-by-step explanation:
The interquartile range is a number that indicates the spread of the middle half, or the middle 50 percent of the data. It is the difference between the third quartile (Q3) and the first quartile (Q₁). The IQR for this data set is calculated as 9 minus 2, or 7.