Interquartile range

The interquartile range reports the range of the middle 50% of data values. It is the distance between the first and third quartiles. It helps us to understand how spread out the data values are. On a quiz, the grades were {71, 82, 85, 85, 87, 91, 93, 95, 98, 98, 100} The range is 100-71=29, but the first quartile is 85 and the third quartile is 98, making the interquartile range 98-85=13. The middle 50% of data values cover a range of 13 points.