## Statistical Graphs Statistics is concerned with the collection, presentation and analysis of quantities of information and data.
This information can then be used to make conclusions and predictions.

Once data has been collected, it can be shown in tables and graphs.

The following types of graph can be used. Care must be taken to ensure that each graph has a title, labelled axes and appropriate scales, with units where necessary.

To show the various types of graphs, the following set of data will be used to show how a group of school pupils travel to school.

 Means of transport Bus Car Foot Bicycle Number of pupils using this type of transport 24 6 18 12

### Pictographs

 Pictographs represent the information with pictures. How pupils travel to school Scale: Each picture represents 6 pupils Bus   Car   Foot   Bicycle

### Column graph

(This is sometimes called a bar or block graph.)

• The height of the column is proportional to the number of times each event occurs.
• The thickness of each column is the same.
• The bars could also be drawn horizontally. Pie graph

This is sometimes called a pie chart or sector graph.

• A circle is divided into sectors. The angle of each sector represents the fraction each event is out of the total number of events.
• Pie graphs require calculations and the use of protractors.

In our example, as there are 60 people, each person is shown by 360° 60° = 6°

This means that:

 Bus needs an angle of 24 × 6°= 144° Car needs an angle of 6 × 6° = 36° Foot needs an angle of 18 × 6° = 108° Bicycle needs an angle of 12 × 6°= 72° See an interactive example of a pie chart − (This activity was produced by the Shodor Education Foundation.)

### Time Series

time series graph is a line graph of repeated measurements taken over regular time intervals.

Time is always shown on the horizontal axis.

On time series graphs data points are drawn at regular intervals and the points joined, usually with straight lines.

Time series graphs help to show trends or patterns.

e.g. Polar Cream Ltd, an ice cream company, shows its sales over the past three years, taken every three months, on the time series graph below. (Quarter 1 is for January, February and March) From the graph it can be seen that ice cream sales are seasonal (high in summer-low in winter).
There would also seem to be a trend towards higher sales each year.