Comparing box plots without using values
"The Vague Comparison"
The Mistake in Action
Compare the two distributions shown in the box plots.
Wrong: "Class A has a bigger spread. Class B did better."
Why It Happens
Students make general statements without referencing specific values from the diagrams. This loses marks for interpretation.
The Fix
Always quote values when comparing box plots:
Good comparison: "Class B has a higher median (57%) than Class A (40%), showing Class B performed better on average.
Class A has a larger IQR (30 compared to 20), meaning Class A's results were less consistent.
Class A has a larger range (70 compared to 55), showing more variation overall."
Use: median, IQR, range, minimum, maximum — with actual numbers.
Spot the Mistake
Can you identify where this student went wrong?
Compare the distributions
Class A has bigger spread, Class B did better
Click on the line that contains the error.
Related Topics
Learn more about the underlying maths: