A Frequency diagrams also called a histogram is used to display grouped continuous data. It differs from a bar graph in that the bars touch and that bar graphs are only used to display qualitative data or discrete numerical data.
The following points should be considered when drawing frequency diagrams for grouped continuous data:
- Class intervals should go on the horizontal axis
- Frequencies should go on the vertical axis
- The highest and lowest possible values in each interval go at either ends of the bar
- The bars must be joined together, to indicate that the data is continuous