Bar charts
A bar chart, like a A vertical bar graph used to represent the frequencies of certain ranges or intervals. The data values must be numerical and grouped., shows the frequency of events occurring. The height of the bar is the frequency.
A simple bar chart may look like this.
Comparative bar charts
Bar charts may be needed to compare data.
The following frequency table shows the information for the numbers of pets owned by a class.
| No pets | 1 pet | 2 pets | 3 or more pets | |
| Boys | 2 | 4 | 2 | 3 |
| Girls | 3 | 3 | 2 | 1 |
| Boys | |
|---|---|
| No pets | 2 |
| 1 pet | 4 |
| 2 pets | 2 |
| 3 or more pets | 3 |
| Girls | |
|---|---|
| No pets | 3 |
| 1 pet | 3 |
| 2 pets | 2 |
| 3 or more pets | 1 |
A comparative bar chart can show this information. A key that shows which bar represents which data is necessary to be able to read the bar chart properly.