Bar Charts & Pictograms (Edexcel IGCSE Maths A (Modular))

Revision Note

Flashcards

Bar Charts & Pictograms

What is a bar chart?

  • 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

Bar chart showing shoe sizes in a class
  • 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 dual bar chart showing the number of hot food items and ice creams sold each month for February, March, and April

What is a pictogram?

  • 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

A pictogram showing shoe sizes in a Year 11 class
  • 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

Examiner Tips and Tricks

  • 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

Worked Example

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 dual bar chart showing the number of pets owned by Year 7 and Year 8 students

(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

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Mark Curtis

Author: Mark Curtis

Expertise: Maths

Mark graduated twice from the University of Oxford: once in 2009 with a First in Mathematics, then again in 2013 with a PhD (DPhil) in Mathematics. He has had nine successful years as a secondary school teacher, specialising in A-Level Further Maths and running extension classes for Oxbridge Maths applicants. Alongside his teaching, he has written five internal textbooks, introduced new spiralling school curriculums and trained other Maths teachers through outreach programmes.

Dan Finlay

Author: Dan Finlay

Expertise: Maths Lead

Dan graduated from the University of Oxford with a First class degree in mathematics. As well as teaching maths for over 8 years, Dan has marked a range of exams for Edexcel, tutored students and taught A Level Accounting. Dan has a keen interest in statistics and probability and their real-life applications.