Box plots, step by step
A box plot says five things about a set of numbers and nothing else.
What is the largest value?
Scores on the spelling test (points)
- A box plot is five numbers drawn to scale — not a bar, and nothing here is a total. Read the five marks off one at a time, and the question answers itself.
- Left whisker end: 10 points — the smallest value.
- Left edge of the box: 30 points — the quarter mark — a quarter of the data is below it.
- Line inside the box: 35 points — the MEDIAN, not the mean and not the middle of the box's width.
- Right edge of the box: 50 points — the three-quarter mark.
- Right whisker end: 55 points — the largest value.
- Now the question. It is asking for the right whisker end, and that has already been read off — no arithmetic is owed.
- So the answer is 55 points. Nothing is added or averaged — a box plot is read, not calculated.
How it works.
- 01
A box plot is five numbers drawn to scale — not a bar, and nothing here is a total. Read the five marks off one at a time, and the question answers itself.
- 02
Left whisker end: 10 points — the smallest value.
- 03
Left edge of the box: 30 points — the quarter mark — a quarter of the data is below it.
- 04
Line inside the box: 35 points — the MEDIAN, not the mean and not the middle of the box's width.
- 05
Right edge of the box: 50 points — the three-quarter mark.
- 06
Right whisker end: 55 points — the largest value.
- 07
Now the question. It is asking for the right whisker end, and that has already been read off — no arithmetic is owed.
- 08
So the answer is 55 points. Nothing is added or averaged — a box plot is read, not calculated.