In Mean plots, size Error Bars using:

Use this parameter to specify the dispersion statistic to use.

Options are listed in the following table:

Select:	When you want to:
Standard Deviation	Use the standard deviation of the mean.
Standard Error of the Mean	Divide the standard deviation by the square root of (n - 1), where n is the sample size.

To Specify the Method for Sizing the Error Bars:

8

Click the radio button corresponding to the method that you want to use.