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Standardized Np Statistic

The Np Statistic, used in Np Charts, can be standardized for use in Short Run Processes as follows:

 

images\conc0119_wmf.jpg 

where n is the sample size, and np-barr is a constant, based on prior data or a desired value.

When based on prior data, np-barr may be calculated as:

 

images\conc0120_wmf.jpg

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