The interquartile range<span> (</span>IQR<span>) is a measure of variability, based on dividing a </span>data set<span>into quartiles. Quartiles divide a rank-ordered </span>data set<span> into four equal parts. The values that divide each part are called the first, second, and third quartiles; and they are denoted by Q1, Q2, and Q3, respectively.</span>
