The interquartile range (IQR) is a statistical measure of the middle values of a sample data set that is separated into four equal parts. This middle-value grouping can provide a median range ...

Semi-interquartile range The semi-interquartile range is half of the difference between the upper quartile and the lower quartile. In the previous example, the quartiles were Q 1 = 4 and Q 3 = 11.