Box Plots

This lesson can be used for revision for the higher Maths GCSE. The examples are quick and concise with exam style questions, go to GCSE Maths if you need more in-depth explanations.

How to draw and use box plots?

Questions that may be asked about box plots:
1) Give you a list to draw a box plot.
2) Give you important pieces of information to draw a box plot.
3) Draw a box plot from a cumulative frequency diagram.
4) Compare distributions by comparing 2 box plots.

Example 1:
Sameena recorded the times, in minutes, some girls took to do a jigsaw puzzle.
Sameena used her results to work out the information in this table.
(a) On the grid, draw a box plot to show the information in the table.
The box plot below shows information about the times, in minutes, some boys took to do the same jigsaw puzzle.
(b) Compare the distribution of the girls' times and the boys' times.

Example 2:
All the students in Mathstown school had a test.
The lowest mark was 18.
The highest mark was 86.
The median was 57.
The lower quartile was 32.
The interquartile range was 38.
On the grid, draw a box plot to show this information.

Example 3:
Harry grows tomatoes.
This year he put his tomato plants into two groups, group A and group B.
Harry gave fertiliser to the tomato plants in group A.
He did not give fertiliser to the tomato plants in group B.
Harry weighed 60 tomatoes from group A.
The cumulative frequency graph shows some information about these weights.
(a) Use the graph to estimate the median.

The 60 tomatoes from group
has a minimum weight of 153 grams
and a maximum weight of 186 grams.
(b) Use this information and the cumulative frequency graph to draw a box plot for the 60 tomatoes from group A.

Harry did not give fertiliser to the tomato plants in group B.
Harry weighed 60 tomatoes from group B.
He drew this box plot for his results.
(c) Compare the distribution of the weights of the tomatoes from group A with the distribution of the weights of the tomatoes from group B. Go to next lesson