Error Bars

These can be used to display additional information, for example the amount of error or uncertainty with each data point.
2003 - On the X Error Bars tab or the Y Error Bars tab
Error bars are usually used in statistical or scientific data
Error bars show potential error or degree of uncertainty relative to each data marker in a series

Error bars express potential error amounts that are graphically relative to each data point
or data marker in a data series.
For example, you could show 5 percent positive and negative potential error amounts in the results of a scientific experiment:
You can add error bars to data series in a 2-D area, bar, column, line, xy (scatter), and bubble charts. For xy (scatter) and bubble charts, you can display error bars for the x values, the y values, or both.
The direction of the error bars depends on the chart type of your chart. For scatter charts, both horizontal and vertical error bars are displayed by default.
You can remove either of these error bars by selecting them, and then pressing DELETE.

To add error bars (for the Y values in an X-Y chart):
Add two columns (or rows) alongside your data; one column contains the value for error above each data point, the second column contains the value for error below each point.
Right-click the data series in your chart and choose Format Data Series
Go to the Y Error Bars tab
Select the Custom radio button
Point the + field to your column of error above values
Point the - field to your column of error below values

These can be added to either or both axes