interquartile math definition
- Definition: Interquartile range is the measure of dispersion which is the difference in the values of two quartiles. The Lower Quartile is denoted as Q 1 and the Upper Quartile is denoted as Q 3. The interquartile range is Q 3 - Q 1. Semi Interquartile range is the midpoint of the interquartile range. In other words, it is one-half of the difference between the third quartile and the first quartile.