STA012 · Probability & statistics · Classes 9–11
Box plot
A box plot shows five numbers: minimum, Q₁, median, Q₃ and maximum. The box holds the middle half of the data; the whiskers reach to the extremes.
⊢▭⊣Box plot
📐 Formula
min — Q₁ [ median ] Q₃ — max
✏️ Worked example
2, 3, 3, 5, 7, 8, 9: whiskers 2 and 9, box from 3 to 8, median line at 5.
🌍 Where it is used
Comparing groups at a glance, spotting skew and outliers.
❓ Quick check
The box in a box plot covers…
🏋️ Practice
EasyFive numbers of 1, 2, 3, 4, 5?
Answer: 1, 1.5, 3, 4.5, 5
MediumLong right whisker means…?
Answer: Right skew (a few high values)
ChallengeWidth of the box equals…?
Answer: The IQR