When the information is shown through a circle, it is called a pie chart. Pie charts are often used when it is necessary to show the relationship of parts to a whole. If you use too many segments in the pie, the impact could be lost. We represent the information in the pie through percentage. In this chart shading may be used to focus special attention on a single element.
Bar graphs are used to display data in a similar way to line graphs. However, rather than using a point on a plane to define a value, a bar graph uses a horizontal or vertical rectangular bar that levels off at the appropriate level.
There are many characteristics of bar graphs that make them useful. Some of these are that:
• They make comparisons between different variables very easy to see.
• They clearly show trends in data, meaning that they show how one variable is affected as the other rises or falls.
• Given one variable, the value of the other can be easily determined.
A histogram is a type of graph that has wide applications in statistics. Histograms allow a visual interpretation of numerical data by indicating the number of data points that lie within a range of values, called a class or a bin. The frequency of the data that falls in each class is depicted by the use of a bar.