Simple charts and graphs
In a nutshell
Simple charts and graphs are used to present data in a visual way so that it is easy to make sense of and compare. You will have already come across most of them: they include pictograms, bar charts, line graphs, twoway tables and stem and leaf diagrams.
Pictograms
Pictograms use images to show frequencies. They have a key which tells you what one image represents.
Example 1
This pictogram shows how many watermelons were sold in a shop throughout the year.
How many watermelons were sold in April?
$8+8+2=\underline{18}$
$66$ Watermelons were sold in total from January to May. How many were sold in February?
Count the number of watermelon in the diagram:
$(7\times8)+(\frac{1}{2}\times8)+(\frac{1}{4}\times8)=62$
Work out the difference:
$6662=\underline4$
Hence there were four watermelons sold in February.
Bar charts
Bar charts have different heights of bar. The height of each bar represents frequency.
Example 2
The bar chart shows the number of juices sold in a cafe and how much each was sold for.
How much was made from selling orange juice?
Work out the height of the orange juice bar and multiply by $£3$:
$80\times £3 = \underline{£240}$
Twoway tables
Twoway tables are used to show two sets of data.
Example 3
This table shows names: Tom and Grace and their favourite things: colour, country, game and food.
 Tom
 Grace

Favourite colour
 Green
 Blue

Favourite country
 France
 England

Favourite game
 Hide and seek
 Tig

Favourite food
 Ice cream
 Pancakes

Reading across and down you can see that Grace's favourite country is England.
Stem and leaf diagrams
Stem and leaf diagrams show data in order. They make it easy to find out quantities such as the mean, median, mode and range.
Example 4
This stem and leaf diagram shows the ages of people watching a tv show.
What is the age of the youngest person watching?
$\underline{13}$
What is the mean age, to two decimal places?
Add up all the ages and divide by the number of ages:
$\frac{\text{all the values added up}}{\text{the number of values}} = \frac{13+15+16+17+17+22+22+23+30+31+39+48}{12}=\frac{293}{12}={24.41666...}$
Round to two decimal places:
$\underline{24.42}$
Line graphs
Line graphs show changes to a measurement over time. They have time on the xaxis and the quantity being measured on the yaxis.
Example 5
This line graph shows the changes in the popularity of the name 'Emma'.
What was the difference between the number of babies called Emma in 1995 and the number in 2010?
Calculate the difference between the biggest and smallest number:
$522=\underline{50}\underline{\text{ thousand}}$