Bar Charts

What Is It Good For?

Bar charts display data by showing relationships of wholes to wholes. When you want to compare a number of objects or show the same object at different points in time, bar charts are particularly useful. These can answer questions such as:

 
• Which river has consistently higher flows?
• Which temperature range is critical for the widest range of fish?

Stacked bar charts (bars divided up into sections) help show proportions and how these change at various points in time or under various conditions. Stacked bar charts help answer questions such as:

 
• Does the planning portion of the budget change during budget cuts?
• Does time spent on paperwork change with various activities?

Important thresholds (e.g., a minimum flow of 300 cubic feet per second) can be shown with a line across all the bars to find fatal flaws quickly.

How Do I Use It?

 
1. Decide on some consistent measurements. The height of the bar for each factor will depend on that measurement.
2. Create a bar chart using these measurements. Many computer programs such as Harvard Graphics will do this for you.
3. Make sure that the elements are clearly labeled. The reader cannot compare elements without knowing the basis for comparison.

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