What is "interquartile range"

n. (context statistics English) The difference between the first and third quartiles; a robust measure of sample dispersion.

In descriptive statistics, the interquartile range (IQR), also called the midspread or middle fifty, or technically H-spread, is a measure of statistical dispersion, being equal to the difference between the upper and lower quartiles, IQR = Q − Q. In other words, the IQR is the 1st quartile subtracted from the 3rd quartile; these quartiles can be clearly seen on a box plot on the data. It is a trimmed estimator, defined as the 25% trimmed range, and is the most significant basic robust measure of scale.

The interquartile range (IQR) is a measure of variability, based on dividing a data set into quartiles. Quartiles divide a rank-ordered data set 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.