Bar charts A bar chart is a graph that displays data as rectangular bars of diff erent heights (or lengths). When drawing graphs, always remember SALT:
Scale Is the scale suitable? Axis Are the intervals equal? Label Are the axes labelled? What are the units of measure? Title What is the purpose of the graph/chart?
Features of a bar chart ●
● ● Favourite fruits
It consists of rectangular bars of equal width. The space between the bars must be the same.
Bars can be marked vertically or horizontally, but normally we use vertical bars.
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The height (or length) of the bar represents the frequency of the corresponding observation.
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A bar chart is used to display categorical and numerical discrete data.
Drawing a bar chart 1
3
40 35 30
25 20
15 10 5
0 Fruit
Draw a horizontal and a vertical axis and give your chart a title.
Divide the axes into appropriate scales, making sure the spacing is even on each axis.
2 4
Label the axes.
Use a ruler to draw each bar, making sure the width of the bars is equal and the gap between each bar is the same.
Worked example 3
Draw a bar chart to represent the data about the hair colours of a group of students shown in the frequency table below. Hair colour
No. of students Solution
18 16 14 12 10 8 6 4 2
Brown Blond Black Red 16
8 12 10
In general, the top line of a frequency table is the horizontal axis, and the bottom line is the vertical axis.