Statistics is concerned with the collection, presentation and analysis of information and data. This statistical data can be displayed in several different forms including tables, diagrams and graphs.
Care must be taken to ensure that each graph has:
The frequency is the number of times each score, event or measurement occurs.
A frequency table is a table in which information or data is arranged in order. Frequency tables make data easier to read and analyse.
A tally can be used to help add up, in groups of five, the number of times an item occurs. Note that
From the frequency table a bar graph can be drawn.
Bar or Column Graphs
Bar or column graphs are usually used for DISCRETE data, usually whole numbers, and the result of a counting process.
Bar graphs can also be drawn horizontally.
Sometimes, when each item has a different value, data has to be grouped together.
A histogram is a graph that is used to show the information from a frequency table of this type.It is similar to a column graph but the bars are always joined together.
To show the pictograph and the pie graph the following set of data will be used to show how a group of 60 school pupils travel to school.
Pictographs or PictogramStatistical graphs in magazines and reports are often drawn using pictures.
This is sometimes called a pie chart or sector graph.
In our example, as there are 60 people, each person is shown by 360° ÷ 60° = 6°
Time Series Graphs
A time series graph is a line graph of repeated measurements taken over regular time intervals.
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).
These graphs are used to clearly show comparisons between different numbers of items. Each item is shown by a dot.
These graphs are also used to show comparisons between different numbers of items. Each part of the bar strip is proportional to the number of items. Strip graphs can also be shown as percentages.