Read a Box Plot

1) Identify the five-number summary

A box plot shows a data set using five key values: minimum, lower quartile (Q1), median, upper quartile (Q3), and maximum. Read these values directly from the ends of the whiskers, the edges of the box, and the line inside the box.

2) Match each part to its meaning

• Left whisker end = minimum
• Left edge of the box = Q1
• Middle line = median
• Right edge of the box = Q3
• Right whisker end = maximum

3) Answer the question carefully

Some questions ask for one value, such as the median or range. Others ask for comparisons, like the interquartile range or which group has greater spread. Use the labels on the plot and read values exactly before calculating.

4) Calculate only what is needed

If you need the range, subtract minimum from maximum. If you need the interquartile range, subtract Q1 from Q3. If you need a comparison, compare the correct features of the plots rather than the lengths by eye alone.

5) Check your result

Make sure your answer fits the scale of the graph and uses the correct part of the box plot. If a calculation is needed, re-read the two values before subtracting.