Quartiles divide a rank-ordered data set into four equal parts. The values that divide each part are called the fist, second, and third quartiles; and they are denoted by Q1,Q2,andQ3, respectively.
- Q1 is the “middle” value in the first half of the rank-ordered data set.
- Q2 is the median value in the set.
- Q3 is the “middle” value in the second half of the rank-ordered data set.
The interquartile range is equal to Q3−Q1.