How to Format Error Bars

Scientists add error bars to graphs to convey statistical information.

When a scientist prepares graphs for a report, she relies on error bars to indicate statistical errors in data measurements. For a standard X-Y graph, each point plots a dependent variable, such as temperature, against an independent one, such as time. The scientist uses the average of many temperature measurements and determines the standard deviation or standard error for these measurements. Vertical error bars on each point show the distribution of data about the average. Using the charting function in Microsoft Excel, you can easily add error bars to graphs.

Things You'll Need

• Microsoft Excel

Instructions

1. Create an X Y line or scatter plot in Excel using the Chart Wizard.

2. Click on the graph line within the Excel chart. This highlights the line itself. In the “Format” menu, select “Selected Data Series.”

3. Click the “Y Error Bars” tab. Select the type of error bars you want for the graph, such as “Both,” “Plus,” “Minus” or “None.” Select the “Error Amount,” such as “Fixed Value,” “Percentage,” “Standard Deviation,” “Standard Error” or the “Custom” option. Set the amount value next to the option.

4. Click the “OK” button to close the formatting window. The graph changes to include error bars.

References

• North Caroline State University: Using Error Bars in Your Graph
• Microsoft: Add Error Bars to a Chart