Bar Charts & Pictograms (Cambridge (CIE) IGCSE Maths)

Revision Note

Written by: Mark Curtis

Reviewed by: Dan Finlay

A bar chart is a visual way to represent discrete data
- Discrete data is data that can be counted
  - This can be numerical like shoe sizes in a class
  - Or non-numerical (categorical) like colours of cars down a road
The horizontal axis shows the different outcomes
The vertical axis shows the frequency
The heights of the bars show the frequency
- Bars should be separated by gaps
- Bars should have equal widths

The mode is the outcome with the highest bar
You can also get dual bar charts to compare two data sets
- Bars are in pairs (side-by-side) for each outcome

A pictogram is an alternative to a bar chart
- It is used in the same situations
There are no axes
- Frequency is represented by symbols
- A key shows the value of 1 symbol
  - For example, 1 symbol represents a frequency of 2
- Half and quarter symbols are often used

The pictogram above shows the shoe sizes of students in a class
- As 1 picture of a shoe represents 2 students
  - Half a shoe represents 1 student
- The number of students with a shoe size of 7, is 3

If asked to draw a bar chart, find the largest frequency and choose a scale which makes that fit in the space provided
If asked to draw a pictogram, pick a symbol that is easy to duplicate and draw half (or quarter) of

Mr Barr teaches students in Year 7 and Year 8.
He records the number of pets that students in each year have.
His results are shown below.

(a) Write down the modal number of pets for his Year 7 students.

The modal number (mode) is the number of pets that occurs the most
Visually, this will be the highest bar for Year 7s

The mode for Year 7 is 1 pet

(b) How many Year 8 students does he teach?

Add up all the heights (frequencies) of the Year 8 bars

4 + 8 + 4 + 3 + 0 + 2

He teaches 21 Year 8 students

Last updated: 7 June 2024

the (exam) results speak for themselves:

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