To estimate the standard deviation for Z-MR chart
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1    Choose Stat > Control Charts > Variables Charts for Individuals > Z-MR > Z-MR Options > Estimate.

2    Under Methods for estimating the standard deviation, How to define groups of observations, choose one of the following:

·    By runs

·    By parts (combine all observations for the same part)

·    Constant (combine all observations)

·    Relative to size (combine all observations, use log)

3    Under For each group, calculate, choose a method to estimate the standard deviation.

3    If you like, use any dialog box options, then click OK.