In a box-and-whisker plot, which part shows the spread between the first and third quartiles?

• A. The whiskers
• B. The outliers
• C. The box
• D. The central line

Answer: (C)

The concept being tested is the interquartile range, the spread of the middle half of the data. In a box-and-whisker plot, this spread is shown by the box itself. The left edge of the box marks the first quartile (Q1) and the right edge marks the third quartile (Q3), so the distance between those edges equals Q3 minus Q1. The line inside the box represents the median, which indicates the middle value, not the spread. The whiskers extend to the minimum and maximum values (within a typical 1.5 IQR rule), and any points beyond are outliers. So the box is the part that shows the spread between the first and third quartiles.