The interquartile range (IQR) is defined as the difference between the first and third quartiles (Q3 − Q1). What feature of the box-and-whisker plot does the IQR describe?

The IQR is Q3 − Q1, which measures the spread of the middle 50% of the data. In a box-and-whisker plot, Q1 and Q3 mark the left and right edges of the box, so their difference is the length of the box. The correct choice is the length of the box of the box-and-whisker plot.

AI-written and checked against the verified answer.